roachtest: fix zipping of artifacts to include other zips

[smg260]

When artifacts are zipped in preparation for being published to
TeamCity, other zip files are skipped. The idea is that we won't try
to recursively zip artifacts.zip itself, or debug.zip, which is
published separately. However, some tests (notably, tpchvec)
download their own zip files in the logs directory so that they'll
be available for analysis when a test fails.

While there was an intention to skip only top-level zip files (as
indicated by existing comments), the code itself would skip any zip
files found in the logs directory. This commit updates the zipping
logic to skip only toplevel zip files, allowing tests to write their
own zip files to the logs directory and have them available for
inspection later.

Release note: None.Backport:

• 1/1 commits from "roachprod: fix target path when getting cluster artifacts." (roachprod: fix target path when getting cluster artifacts. #83923)
• 1/1 commits from "roachtest: fix zipping of artifacts to include other zips" (roachtest: fix zipping of artifacts to include other zips #84085)
• 2/2 commits from "roachtest: refactor github issue posting and expose actual vm args for reporting" (roachtest: refactor github issue posting and expose actual vm args for reporting #87304)
• 1/1 commits from "roachprod: set default cluster settings when starting" (roachprod: set default cluster settings when starting #88716)
• 1/1 commits from "roachtest: use structured errors" (roachtest: use structured errors #88556)
• 3/3 commits from "Roachtest redirect SSH flakes to test-eng" (Roachtest redirect SSH flakes to test-eng #88492)
• 1/1 commits from "Revert fmtsafe.go output" (Revert fmtsafe.go output #90720)
• 1/1 commits from "Roachtest SSH Retries" (Roachtest SSH Retries #90451)
• 1/1 commits from "roachtest: Retry failed SCP attempts in the same way as SSH commands." (roachtest: Retry failed SCP attempts in the same way as SSH commands. #92082)

Please see individual PRs for details.

/cc @cockroachdb/release

[cockroach-teamcity]

This change is