chore!: Update CurrencyRateController to expose all methods through messenger

[GuillaumeRx]

Explanation

This updates the CurrencyRateController to expose all methods through the messenger in a standardized way.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

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Note

Medium Risk
Medium risk because it introduces a breaking rename of the CurrencyRateController get-state action type and changes the controller’s messenger surface area, requiring downstream type/import updates.

Overview
CurrencyRateController now exposes setCurrentCurrency and updateExchangeRate via the messenger by registering method action handlers, and adds generated method action type definitions for these calls.

This standardizes/renames the get-state messenger action type from GetCurrencyRateState to CurrencyRateControllerGetStateAction (type-only breaking change) and updates internal consumers (MultichainAssetsRatesController, TokenSearchDiscoveryDataController, and bridge-controller) plus exports the new action types from assets-controllers.

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