SQL Latency metric

Customers have occasions where developers are opening a transaction receiving a request then calling out to a 3rd party API and waiting for a response then committing the transaction against the DB. They need to find out who these developers are and the new metric will help

**Is your feature request related to a problem? Please describe.**
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

**Describe the solution you'd like**
A clear and concise description of what you want to happen.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.

**Additional context**
Add any other context or screenshots about the feature request here.

Jira issue: CRDB-37300

Start by clarifying the intended SQL latency metric for transactions that wait on a third-party API before committing. The issue names no files, tests, or entry points; done would require an agreed metric definition and a way to identify the developers responsible for these transactions.

Written by the indexing model from the issue text.