[Bug]: transaction metrics does not capture the information if transaction used advance default estimate

In transaction metrics we capture the estimate used for transaction `low / medium / high / custom / dapp-suggested`. But we do not capture information if custom (or advance) estimate used by transaction is the default estimate saved by the user.

Here we can capture metrics at 2 places:
1. as user updates advance default we can capture user setting metrics
2. is transaction created by user is using advance default can be captured in transaction metrics

cc @kevinghim , @brad-decker

Start by locating the transaction metrics entry point and the handling for user-saved advanced default estimates. Trace both settings updates and transaction creation to determine where the estimate source is recorded. Done means metrics capture when a transaction uses the user's default advanced estimate, including the setting update event if applicable.

Written by the indexing model from the issue text.