feat: update BUILT_IN_NETWORKS

[mikesposito]

Explanation

Additional Infura networks have been added in #8680, but the BUILT_IN_NETWORKS object was missed. This object is not used outside of tests in core, though it’s exported by controller-utils and used by clients. This PR adds the networks to BUILT_IN_NETWORKS as well

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

Low Risk
Low risk: adds new entries to exported network constants and updates the changelog; behavior changes only for consumers referencing these newly supported networks.

Overview
Adds the previously-missing Infura mainnet networks (monad-mainnet, zksync-mainnet, megaeth-mainnet, avalanche-mainnet) to BUILT_IN_NETWORKS, including their chainId, ticker, and blockExplorerUrl mappings.

Updates the @metamask/controller-utils changelog entry to reflect the expanded BUILT_IN_NETWORKS coverage.

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