refactor: Refactor keyring controller to use modular init pattern

[Mrtenz]

Description

This refactors the keyring controller to use modular init.

Changelog

CHANGELOG entry:

Related issues

Fixes:

Manual testing steps

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]

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

---

Note

Moves keyring setup from Engine into modular init functions with dedicated messengers, updates Engine to use them, and adds supporting types and tests.

• Engine:
  • Refactors keyring setup to use modular controllers. Removes inlined HdKeyring/LedgerKeyring/QrKeyring builders and direct KeyringController construction and encryptor wiring.
  • Passes initialKeyringState, qrKeyringScanner, and (keyring-snaps) removeAccount into initModularizedControllers and retrieves KeyringController from controllersByName.
  • Adjusts snaps auth/user-storage init placement; minor import cleanups.
• Controllers:
  • Adds keyring-controller-init to construct KeyringController (configures Encryptor, HdKeyring, LedgerKeyring, QrKeyring, and (keyring-snaps) SnapKeyringBuilder).
  • Adds snap-keyring-builder-init to create SnapKeyring builder; persists keyrings via init messenger and uses removeAccount helper.
• Messengers:
  • Adds keyring-controller-messenger and snap-keyring-builder-messenger (plus init messenger) and registers them in messengers/index.
• Types/Utils:
  • Extends engine types and init request to include initialKeyringState, qrKeyringScanner, and (keyring-snaps) removeAccount; adds KeyringController and SnapKeyringBuilder to controller maps.
  • Updates test utils to provide new init request fields.
  • Enhances SnapKeyringBuilder interface (name/state metadata).
• Tests:
  • Adds unit tests for keyring init and messengers; updates modular init tests to include new controllers.

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[sonarqubecloud]

Quality Gate failed

Failed conditions
79.4% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud

[ccharly]

Nit: Cosmetic:

Suggested change

	qrKeyringBuilder.type = QrKeyring.type;
	qrKeyringBuilder.type = QrKeyring.type;

[ccharly]

Nit: Cosmetic:

Suggested change

[ccharly]

Nit: Cosmetic:

Suggested change