feat(profile-sync-controller): add profile pairing & canonical profile id management

[mathieuartu]

Explanation

References

• https://consensyssoftware.atlassian.net/browse/MUL-1722

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

Medium Risk
Touches SRP authentication/sign-in flow by adding a new profile-pairing API call and new profile ID semantics, which could affect login/session state and downstream storage key derivation if mishandled.

Overview
Adds SRP profile pairing during AuthenticationController.performSignIn: when 2+ SRPs are present it calls POST /profile/pair, propagates the returned canonical profile ID across all srpSessionData entries, and emits a new AuthenticationController:profileSignIn event when aliases are returned or the canonical ID changes (pairing failures are treated as non-fatal).

Extends auth SDK types and services to support pairing and canonical IDs: UserProfile gains canonicalProfileId, ProfileAlias is introduced, SRP /srp/login now sends X-MetaMask-Profile-Pairing: enabled and parses profile_aliases, and SRP login resolves/stores the original per-SRP profileId from aliases via new computeIdentifierId hashing utility.

Updates fixtures/mocks and expands unit tests to cover pairing behavior, event emission, header usage, alias parsing, and canonical/original profile ID persistence.

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