feat(snap-networks-utils): add shared RemoteFeatureFlagProvider

[ulissesferreira]

This pull request introduces a new RemoteFeatureFlagProvider utility to the snap-networks-utils package, enabling access to remote feature flags via a messenger interface. The provider is fully tested and integrates with the @metamask/remote-feature-flag-controller package, which is added as a new dependency.

New Remote Feature Flag Provider

• Added the RemoteFeatureFlagProvider class, which exposes methods to fetch individual or multiple remote feature flag values using an injected messenger. This enables other code to easily query LaunchDarkly/client-config feature flags.
• Defined supporting types and constants for the provider, including RemoteFeatureFlagProviderMessenger and REMOTE_FEATURE_FLAG_PROVIDER_NAME, to ensure type safety and integration with the messenger system.

Testing

• Added comprehensive tests for RemoteFeatureFlagProvider, covering both single and multiple flag retrieval, including cases for missing keys and empty input.

Dependency Updates

• Added @metamask/remote-feature-flag-controller as a new dependency in package.json to support the new provider.## Explanation

References

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

[ulissesferreira]

@metamaskbot publish-preview

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@metamask-previews/bitcoin-wallet-snap@2.0.0-preview-a0892371
@metamask-previews/snap-networks-utils@0.0.0-preview-a0892371
@metamask-previews/tron-wallet-snap@2.0.0-preview-a0892371