chore(assets-controllers): add isDeprecated to TokenDetectionController

[Prithpal-Sooriya]

Explanation

As part of the assets-unify-state rollout, legacy asset controllers need an opt-in deprecation path so hosts can disable them when AssetsController supersedes their behavior — without removing the controllers yet.

This PR adds an optional isDeprecated constructor callback to TokenDetectionController, following the same pattern already used by TokensController, CurrencyRateController, TokenListController, and the multichain controllers. When isDeprecated() returns true:

• Polling is stopped immediately
• All detection entry points become no-ops (detectTokens, addDetectedTokensViaWs, addDetectedTokensViaPolling, start, _executePoll, and event-driven restarts)
• The callback is re-evaluated on every entry point so it can be toggled at runtime

This is behavior-preserving when the callback is omitted or returns false (the default).

References

• ASSETS-3337
• Extension reference: fix: delete token list metamask-extension#43108
• Core reference pattern: feat: disable token list #8945

Manual testing steps

N/A — behavior-preserving when isDeprecated is not provided.

Screenshots/Recordings

N/A

Changed files

File	Change	Verification
packages/assets-controllers/src/TokenDetectionController.ts	Added isDeprecated option and guards at all entry points	ESLint pass
packages/assets-controllers/src/TokenDetectionController.test.ts	Added isDeprecated test suite (9 tests)	yarn workspace @metamask/assets-controllers run jest --no-coverage packages/assets-controllers/src/TokenDetectionController.test.ts -t "isDeprecated" — all pass
packages/assets-controllers/CHANGELOG.md	Added Unreleased entry	Reviewed against Keep a Changelog format

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