feat: replace assets state references confirmations (#29726)

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## **Description**

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The new `AssetsController` is being introduced to replace most
controllers from `@metamask/assets-controllers`. This is one of many PRs
that replace direct access to legacy state with selectors that, using a
feature flag, handle the transition between the legacy state and the new
state when the flag is turned on.

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## **Related issues**

Fixes: https://consensyssoftware.atlassian.net/browse/ASSETS-2827

## **Manual testing steps**

```gherkin
Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]
```

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- [X] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask Mobile
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guidelines](https://github.com/MetaMask/metamask-mobile/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

#### Performance checks (if applicable)

- [ ] I've tested on Android
  - Ideally on a mid-range device; emulator is acceptable
- [ ] I've tested with a power user scenario
- Use these [power-user
SRPs](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/edit-v2/401401446401?draftShareId=9d77e1e1-4bdc-4be1-9ebb-ccd916988d93)
to import wallets with many accounts and tokens
- [ ] I've instrumented key operations with Sentry traces for production
performance metrics
- See [`trace()`](/app/util/trace.ts) for usage and
[`addToken`](/app/components/Views/AddAsset/components/AddCustomToken/AddCustomToken.tsx#L274)
for an example

For performance guidelines and tooling, see the [Performance
Guide](https://consensyssoftware.atlassian.net/wiki/spaces/TL1/pages/400085549067/Performance+Guide+for+Engineers).

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<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Updates how native balances are looked up for
`gas_insufficient_native_asset`, which could change metrics output if
address casing/normalization differs across callers. Scoped to
analytics/metrics code with test adjustments, but affects
transaction-finalized event properties.
> 
> **Overview**
> Updates gas metrics to read account balances via the
`selectAccountsByChainId` selector instead of directly accessing
`AccountTrackerController` state, aligning with the ongoing assets-state
migration.
> 
> `getNativeBalance` now resolves the sender address with
`safeToChecksumAddress` and looks up balances by checksummed key
(removing the previous `.toLowerCase()` access). Tests were updated to
use a realistic checksummed address and store balances under that exact
key.
> 
> <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit
f71e6c6. Bugbot is set up for automated
code reviews on this repo. Configure
[here](https://www.cursor.com/dashboard/bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: bergarces

app/core/Engine/controllers/transaction-controller/metrics_properties/gas.test.ts

@@ -14,18 +14,20 @@ const mockGetNativeTokenAddress = getNativeTokenAddress as jest.MockedFunction<
   typeof getNativeTokenAddress
 >;
 
+const MOCK_CHECKSUMMED_ADDRESS = '0x44934055428d2eF7E3F97D98187f2459007fa49F';
+
 const createMockState = (
   balance: string = '0x100000000000000000',
   chainId: string = '0x1',
-  address: string = '0xuser',
+  address: string = MOCK_CHECKSUMMED_ADDRESS,
 ): RootState =>
   ({
     engine: {
       backgroundState: {
         AccountTrackerController: {
           accountsByChainId: {
             [chainId]: {
-              [address.toLowerCase()]: { balance },
+              [address]: { balance },
             },
           },
         },
@@ -40,7 +42,11 @@ const createMockRequest = (
   eventType: TRANSACTION_EVENTS.TRANSACTION_FINALIZED,
   transactionMeta: {
     chainId: '0x1',
-    txParams: { from: '0xuser', gas: '0x5208', gasPrice: '0x1' },
+    txParams: {
+      from: MOCK_CHECKSUMMED_ADDRESS,
+      gas: '0x5208',
+      gasPrice: '0x1',
+    },
     ...overrides,
   } as TransactionMeta,
   allTransactions: [],
@@ -139,7 +145,7 @@ describe('getGasMetricsProperties', () => {
     const request = createMockRequest(
       {
         txParams: {
-          from: '0xuser',
+          from: MOCK_CHECKSUMMED_ADDRESS,
           gas: '0x5208',
           gasPrice: '0x100000000000000000',
         },
@@ -156,7 +162,11 @@ describe('getGasMetricsProperties', () => {
     const state = createMockState('0x100000000000000000');
     const request = createMockRequest(
       {
-        txParams: { from: '0xuser', gas: '0x1', gasPrice: '0x1' },
+        txParams: {
+          from: MOCK_CHECKSUMMED_ADDRESS,
+          gas: '0x1',
+          gasPrice: '0x1',
+        },
       },
       state,
     );

app/core/Engine/controllers/transaction-controller/metrics_properties/gas.ts

@@ -11,6 +11,8 @@ import type {
   TransactionMetricsBuilderRequest,
 } from '../types';
 import type { RootState } from '../../../../../reducers';
+import { selectAccountsByChainId } from '../../../../../selectors/accountTrackerController';
+import { safeToChecksumAddress } from '../../../../../util/address';
 
 export function getGasMetricsProperties({
   transactionMeta,
@@ -88,10 +90,13 @@ function getNativeBalance(
   chainId: string,
   address: string,
 ): BigNumber {
-  const accountsByChainId =
-    state.engine?.backgroundState?.AccountTrackerController?.accountsByChainId;
+  const accountsByChainId = selectAccountsByChainId(state);
 
-  const account = accountsByChainId?.[chainId]?.[address?.toLowerCase()];
+  const checksummedAddress = safeToChecksumAddress(address);
+  const account =
+    checksummedAddress !== undefined
+      ? accountsByChainId?.[chainId]?.[checksummedAddress]
+      : undefined;
 
   return new BigNumber((account?.balance as Hex) ?? '0x0');
 }