feat(assets-controllers): seed mUSD as default tracked asset

[salimtb]

Adds mUSD (0xaca92e438df0b2401ff60da7e4337b687a2435da) as a default tracked token for all accounts on Ethereum mainnet (0x1), Linea (0xe708), Monad mainnet (0x8f), and Monad testnet (0x279f).

TokensController changes:

• Directly seeds mUSD into allTokens state for all known accounts at construction time, from persisted state, and on these events:
  • KeyringController:unlock — covers post-unlock account availability
  • AccountsController:accountAdded — covers async account loading
  • AccountsController:selectedEvmAccountChange — covers account switching
  • NetworkController:networkAdded — covers newly added supported chains
  • NetworkController:stateChange patches (op: add) — detects chain additions

TokenDetectionController changes:

• start() now calls #seedDefaultTokens() which uses the TokensController:addTokens action per supported chain, ensuring mUSD is seeded via the standard deduplication path on every detection run
• Re-seeds when the selected EVM account changes or a supported chain is added
• #defaultTokensSeeded flag prevents redundant seeding within a session

Tests:

• Added 13 tests for mUSD seeding triggers in TokensController
• Updated messenger event delegation and helpers for new event types

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

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Note

Medium Risk
Touches token state seeding and network/account event handling, which can affect users’ persisted allTokens and default asset visibility across chains. Logic is largely additive and guarded/deduped, but incorrect triggers or chain lists could lead to unexpected token entries or missed seeding.

Overview
Adds automatic seeding of MetaMask USD (mUSD) into TokensController state so it appears as a default tracked token on supported chains, including seeding for existing/persisted accounts and re-seeding on account selection, account creation, unlock, and supported network additions (both networkAdded and stateChange add patches).

Updates TokenDetectionController.start() to seed mUSD via TokensController:addTokens per configured supported chain, guarded by a per-session flag and re-triggered on selected-account changes and supported NetworkController:networkAdded.

Expands TokensController/TokenDetectionController messenger allowed events accordingly, updates/extends TokensController tests heavily (mUSD seeding scenarios plus a few behavioral test additions like watchAsset passing pageMeta, updating existing tokens via addDetectedTokens, safer handling when network patches omit networkConfigurationsByChainId, and ERC721 detection when supportsInterface throws), and removes an eslint suppression for explicit return types in TokensController.test.ts.

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