chore(lint): Fix suppressed ESLint errors in network-controller package

[Mrtenz]

Explanation

This fixes all suppressed ESLint errors in the network-controller package.

References

Closes #7377.

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

Adds explicit return types and stricter typings throughout network controller, network client creation, and RPC service code (plus tests), with minor internal refactors and no intended behavior changes.

• Network Controller
  • Add explicit return types to methods (enableRpcFailover, lookupNetwork, setProviderType, etc.) and helpers (isValidUrl, validateInitialState, knownKeysOf).
  • Type selectors and proxies; annotate selectNetworkConfigurationsByChainId return; initialize networksMetadata via ??=.
  • Refactor updateNetwork RPC endpoint ops: reorder add/replace branches; no logic change intended.
  • Overload/return typing for initializeProvider; tighten private method signatures and event listener types.
  • JSDoc/lint adjustments (e.g., EIPS naming convention suppression).
• Network Client Creation
  • Strongly type createAutoManagedNetworkClient proxies and options; default getBlockTrackerOptions typing.
  • Add return types and stricter generics in create-network-client helpers (block tracker, middleware, RPC chain).
• RPC Service/Chain
  • Type event registration methods to return disposable handles; expose concrete return types; import IDisposable.
  • Add explicit types for utility functions and public methods (resetPolicy, getCircuitState, event hooks).
• Tests & Helpers
  • Update tests to use PollingBlockTrackerOptions, RpcServiceOptions, SinonFakeTimers, Json; fix promisify binding for ethQuery.sendAsync.
  • Add precise function return types and narrow generics in test utilities; minor eslint disables where needed.

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