To reduce log noise in local test runs:
- move the `buildinfo.txt` dump and header info lines
`OS:`, `Perl:`, `diff:` behind a `--ci` `runtests.pl` option.
- enable this option for the CI test targets.
- hide `Env:` header info line if empty.
- merge `Env:` output into a single `logmsg()` call.
Closes#18147
In an attempt to make them easier to find.
The man pages runtests.md and testcurl.md are in /docs
The rest of the test documentation is in /docs/tests
Closes#17463
