chore: Expose missing MoneyAccountService methods through the messenger

[GuillaumeRx]

Explanation

This exposes missing methods used in the clients through the messenger.

References

Progresses https://consensyssoftware.atlassian.net/browse/WPC-989

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

Low Risk
Low risk: this only exposes an existing MoneyAccountController.init method via the messenger and adds the corresponding action type, without changing account/keyring logic.

Overview
Exposes the previously unexposed MoneyAccountController:init method through the controller messenger by adding init to MESSENGER_EXPOSED_METHODS.

Adds the corresponding MoneyAccountControllerInitAction type, exports it from the package entrypoint, and documents the new exposed action in the changelog.

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