sql,obs: metrics / logs that break down SQL errors by group or type

**Is your feature request related to a problem? Please describe.**

Currently, when investigating SQL errors, it is difficult to determine the types of errors being returned to the client, without diving deep into debug.zip internals.

We already have a `SQL Statement Errors` chart on the SQL dashboard of the DB Console. However, it only shows a total. This makes it hard to deduce the class of errors.

**Describe the solution you'd like**

Ideally, we'd be able to easily tell the class of errors that are being returned to the SQL client. This could be metrics, or logs.

The latter could be very verbose / expensive. Perhaps these could be gated behind a vmodule / sampling.

Having metrics per error code would also be pretty noisy. Maybe we can bucket different error codes together.

**Additional context**

This came up in the context of https://github.com/cockroachlabs/support/issues/2869.

[Another (internal) thread.](https://cockroachlabs.slack.com/archives/C06PEGL22UX/p1713377268023889?thread_ts=1713376763.344529&cid=C06PEGL22UX)

Jira issue: CRDB-38026

Epic CRDB-380