fix: fix re-use string for user-ops sender/to (#465)

We recently narrowed the type used for `EthAddressStruct` to be `Hex`.
This actually have a huge impact on various types that depend on it.

While most of the account types are fine, the user-ops one also bubbles
up to the `TransactionController` and would require a bit more refactor
to re-type everything correctly.

For now, we'll just revert to what it was and keep them as `string` for
those types.

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> **Medium Risk**
> Touches shared Ethereum address validation/types, which can ripple
through downstream type inference and RPC param validation; behavior
should be mostly compatible but type-level impacts are broad.
> 
> **Overview**
> Reverts `EthAddressStruct`’s inferred type back to `string` (while
keeping the same `0x…{40}` validation regex) to undo an unintended
breaking change that propagated into ERC-4337/user-op address-like
fields.
> 
> Introduces `EthAddressStrictStruct` (Hex-typed) for callers that need
strict `Hex` inference, and updates EIP-7702 authorization tuple
validation to use this stricter struct. The changelog documents the
revert and notes `21.4.0` will be yanked.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
2b1eb24. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: ccharly

packages/keyring-api/CHANGELOG.md

@@ -7,6 +7,18 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add `EthAddressStrictStruct` struct and `EthAddressStrict` types ([#465](https://github.com/MetaMask/accounts/pull/465))
+  - This is a stricter variant of `EthAddressStruct` which uses `Hex` instead of `string` for its inferred type.
+
+### Changed
+
+- Re-use `string` for ERC4337 address-like fields ([#465](https://github.com/MetaMask/accounts/pull/465))
+  - This change reverts that and keeps using `string` for all address-like types.
+  - Changes in [#405](https://github.com/MetaMask/accounts/pull/405) updated the associated type for `EthAddressStruct` from `string` to `Hex`, this was actually a small breaking change that went unnoticed and that would require some effort to adapt in upstream clients/controllers, for this reason, we are undoing this change for now.
+  - Version [21.4.0] will be marked as **YANKED**, consumers are expected to use this new version that reverts this breaking change.
+
 ## [21.4.0]
 
 ### Added

packages/keyring-api/src/eth/rpc/params.ts

@@ -23,7 +23,11 @@ import {
   unknown,
 } from '@metamask/superstruct';
 
-import { EthAddressStruct, EthBytesStruct } from '../types';
+import {
+  EthAddressStrictStruct,
+  EthAddressStruct,
+  EthBytesStruct,
+} from '../types';
 
 /**
  * A struct for validating Ethereum transaction data.
@@ -118,7 +122,7 @@ export type EthEncryptedData = Infer<typeof EthEncryptedDataStruct>;
  */
 export const EthEip7702AuthorizationStruct = tuple([
   number(), // chainId
-  EthAddressStruct, // address (contract to delegate to)
+  EthAddressStrictStruct, // address (contract to delegate to)
   number(), // nonce
 ]);
 

packages/keyring-api/src/eth/types.ts

@@ -12,9 +12,12 @@ import {
 
 export const EthBytesStruct = definePattern('EthBytes', /^0x[0-9a-f]*$/iu);
 
-export const EthAddressStruct = definePattern<Hex>(
-  'EthAddress',
-  /^0x[0-9a-f]{40}$/iu,
+const ETH_ADDRESS_REGEX = /^0x[0-9a-f]{40}$/iu;
+export const EthAddressStruct = definePattern('EthAddress', ETH_ADDRESS_REGEX);
+// Stricter struct that uses `Hex` as final type.
+export const EthAddressStrictStruct = definePattern<Hex>(
+  'EthAddressStrict',
+  ETH_ADDRESS_REGEX,
 );
 
 export const EthUint256Struct = definePattern(