feat: MUSD-681: (money-account-balance-service) replace constructor config with remote feature flag subscription

[Matt561]

Explanation

This PR updates the @metamask/money-account-balance-service to use a remote vault config instead of constructor args.

References

• MUSD-681: Support remote vault config feature flag in Money Balance Service

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