fix: cp-7.57.2 remove currency rates multichain

[salimtb]

Description

This PR removes the RatesController to reduce redundant CryptoCompare API calls in the multichain architecture.

Reason for the change

The RatesController was introduced for fetching cryptocurrency conversion rates (primarily for BTC and SOL) to support non-EVM chains. However, this resulted in duplicate API calls to CryptoCompare since we already have MultichainAssetsRatesController and TokenRatesController handling rate fetching functionality. This redundancy increased API usage unnecessarily.

Improvement/solution

• Removed RatesController initialization and configuration from the Engine
• Deleted RatesController messenger setup and related controller initialization files
• Removed multichain selectors that depended on RatesController state (selectMultichainConversionRate, selectMultichainCoinRates)
• Cleaned up type definitions and state management to remove RatesController references
• Updated test snapshots and initial background state

The existing MultichainAssetsRatesController and TokenRatesController will continue to handle all rate-fetching needs without the additional overhead of RatesController.

Changelog

CHANGELOG entry: Removed redundant RatesController to optimize API usage

Related issues

Fixes:

Manual testing steps

Feature: Multichain rate fetching

  Scenario: User views portfolio balance with non-EVM accounts
    Given user has Bitcoin and Solana accounts configured
    And user is viewing their portfolio

    When the app fetches cryptocurrency rates
    Then rates should be fetched only through MultichainAssetsRatesController
    And no redundant API calls should be made to CryptoCompare
    And account balances should display with correct fiat conversions

  Scenario: User switches between EVM and non-EVM accounts
    Given user has both EVM and non-EVM accounts
    And user is viewing their wallet

    When user switches between different account types
    Then appropriate conversion rates should display for each account
    And rate updates should continue to work correctly

Screenshots/Recordings

Before

After

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Pre-merge reviewer checklist

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---

Note

Removes RatesController across Engine, messengers, selectors, and types; adds migration 106 to purge its persisted state; updates tests and fixtures.

• Engine/Core:
  • Remove RatesController initialization, context exposure, polling, and state-change subscriptions in Engine.ts and constants.ts.
  • Drop rates-controller-init and its tests; delete rates-controller-messenger and references in messengers/index.ts.
• Selectors:
  • Remove selectMultichainConversionRate and selectMultichainCoinRates; update multichain.ts and related tests accordingly.
• Types:
  • Strip RatesController types and entries from types.ts (controllers, state, actions/events, controller names).
• Migration:
  • Add migration 106 to remove backgroundState.RatesController; register in migrations/index.ts with tests.
• Tests/Fixtures:
  • Update snapshots and initial-background-state.json to omit RatesController.
  • Adjust Engine.test.ts assertions to no longer expect RatesController.

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[github-actions]

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[sahar-fehri]

I think we should also remove useCurrencyRatePolling(chainParams) from the PollingProvide?

[salimtb]

Should we also remove useCurrencyRatePolling(chainParams) from the PollingProvide?

i think this one is needed for evm since it's using the CurrencyRatesController and not RatesController

[sonarqubecloud]

Quality Gate passed

Issues
4 New issues
2 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Cal-L]

LGTM