CI: misc improvements, restore VS2008 job

CI: misc improvements, restore VS2008 job

- appveyor: restore VS2008 job, after fixing its issues.
  Enable OpenSSL in it. It takes 1 minute.
  Follow-up to 9b0467b169e08b70077f09313975d4eac14a9930 #16453
  Follow-up to edfa537100d6b5d2ac1b829c66757880afe59407 #16456
- appveyor: make a copy of OpenSSL DLLs to have them picked up as an
  artifact (disabled by default) to aid local tests.
- appveyor: dump CMake configuration logs on failure.
- appveyor: tidy up job parameter defaults.
- GHA/windows: add pre-fill check option for dl-mingw jobs.
- GHA/windows: fix pre-fill check option for MSYS jobs by installing
  `diffutils`.
  Follow-up to e7adf3e83747c2915c671f2e560cde6f3d4a4905 #15841
- GHA/windows: de-duplicate to `PATH` commands for Cygwin.
- GHA/windows: drop `$SYSTEMROOT/System32` from `PATH` for Cygwin
  configure. It's not needed.
  Follow-up to 36fd2dd6ee874726c628e67fcf6415a2e52bfe29 #13599
- list `.pdb` files in curl version step for MSVC.
  Ref: #16439

Cherry-picked from #16394
Closes #16458