feat: add types for unified bridge ui (MetaMask#5783)

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Adds `isUnifiedUIEnabled` flag to `ChainConfiguration` feature-flag type
and update validators accordingly. This is required as we are adding a
feature flag to support the development of a unified bridge/swap UI.

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## Changelog

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## Checklist

- [x] I've updated the test suite for new or updated code as appropriate
- [x] I've updated documentation (JSDoc, Markdown, etc.) for new or
updated code as appropriate
- [x] I've communicated my changes to consumers by [updating changelogs
for packages I've
changed](https://github.com/MetaMask/core/tree/main/docs/contributing.md#updating-changelogs),
highlighting breaking changes as necessary
- [x] I've prepared draft pull requests for clients and consumer
packages to resolve any breaking changes

Author: ghgoodreau

packages/bridge-controller/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Added optional `isUnifiedUIEnabled` flag to chain-level feature-flag `ChainConfiguration` type and updated the validation schema to accept the new flag ([#5783](https://github.com/MetaMask/core/pull/5783))
 - Add and export `calcSlippagePercentage`, a utility that calculates the absolute slippage percentage based on the adjusted return and the sent amount ([#5723](https://github.com/MetaMask/core/pull/5723)).
 - Error logs for invalid getQuote responses ([#5816](https://github.com/MetaMask/core/pull/5816))
 

packages/bridge-controller/src/types.ts

@@ -64,6 +64,7 @@ export type ChainConfiguration = {
   isActiveDest: boolean;
   refreshRate?: number;
   topAssets?: string[];
+  isUnifiedUIEnabled?: boolean;
 };
 
 export type L1GasFees = {

packages/bridge-controller/src/utils/validators.ts

@@ -59,6 +59,7 @@ export const validateFeatureFlagsResponse = (
     isActiveDest: boolean(),
     refreshRate: optional(number()),
     topAssets: optional(array(string())),
+    isUnifiedUIEnabled: optional(boolean()),
   });
 
   const PlatformConfigSchema = type({