cli: use ExecerContext and companions in sql_util.go

[tbg]

When porting the node status command over to use SQL, we were unable to use context-based cancellation since there is an unaddressed TODO to switch to ExecerContext (etc) in sqlConnI. We worked around that using SET statement_timeout=x but that's just a crutch.

See #25094 (comment).

@knz for triage.

Jira issue: CRDB-6358

[tbg]

I just ran into a problem with QueryRowContext in the context of #25837 where I cancelled a context and it had no effect, which led to this illuminating comment from @knz:

two things
first I think the API that enables context cancellation is actually not used here (something to do with which variant of go's sql stuff and lib/pq are in use)
Also I am not sure our SQL server-side is able to recognize when a client conn drops while a query is running (I think it only picks up the cancellation when the current stmt finishes - not sure)

Especially the former seems troubling. If something takes a context, we expect context cancellation to work. Had we had the contexted API available in #25094 (see link above) we likely would've messed it up (well, hopefully a test would've caught the problem).

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