release-25.1: explain: show "execution time" on EXPLAIN ANALYZE output

[yuzefovich]

Backport 1/1 commits from #143857.

/cc @cockroachdb/release

---

We've been tracking "execution time" statistic for most operators (except for vectorized KV-reading ones which get separate "KV time" stat) for many years now, but for some reason we only reported it on the DistSQL diagram. This commit fixes that oversight so that the stat is now included on EXPLAIN ANALYZE output when available.

Fixes: #143443.

Release note (sql change): New statistic execution time is now reported on EXPLAIN ANALYZE output for most operators. It was previously only available on the DistSQL diagrams (included in EXPLAIN ANALYZE (DISTSQL) output).

Release justification: low-risk observability improvement.

[blathers-crl]

Thanks for opening a backport.

Please check the backport criteria before merging:

• Backports should only be created for serious
  issues or test-only changes.
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If your backport adds new functionality, please ensure that the following additional criteria are satisfied:

• There is a high priority need for the functionality that cannot wait until the next release and is difficult to address in another way.
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Also, please add a brief release justification to the body of your PR to justify this
backport.

[cockroach-teamcity]

This change is 

[mgartner]

Reviewed 19 of 19 files at r1, all commit messages.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @michae2)