fix: Add userFeeLevel as dappSuggested initially when txParams contains gas values for legacy transactions

[OGPoyraz]

Explanation

This PR aims to add userFeeLevel as dappSuggested initially when txParams contains gas values also for legacy transactions.

References

• Issue found while implementing gas modal: feat: Implement redesigned gas fee modal metamask-mobile#15234

Changelog

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, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes