feat(transaction-controller): support saved gas fee levels

[pedronfigueiredo]

Explanation

This expands transaction-controller saved gas fee handling so clients can resolve saved preferences with full transaction metadata instead of only a chain ID. That lets consumers key saved gas settings by both chain and account while keeping the controller API responsible for applying saved fees.

The saved gas payload now supports gas fee estimate levels (low, medium, high) and legacy custom gasPrice values in addition to EIP-1559 custom fee values. Saved estimate levels reuse the current gas fee flow estimate for the saved level; custom values override only the specific saved fields.

Transactions that already include gas fee params continue to use those initial params, so dapp-proposed fees keep precedence over saved preferences. Swap transaction types continue to skip saved gas fees.

References

Related to MetaMask extension work to reintroduce saved gas settings per account and per chain.

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 client adoption work to resolve them