GHA: fix and tweak installed packages for http3-linux and Windows-cross

GHA: fix and tweak installed packages for http3-linux and Windows-cross

- explicitly install `libldap-dev` to not rely on test-specific packages
  installing it implicitly, to have the same `curl -V` output for each
  TLS backend build pair.
  Follow-up to 0455d8772a1af20ce63c46c5738582aa9b1b8441 #18509

- install `libev-dev` for tests. It's a runtime dependency for
  the local build of `nghttpx`. Missing it made pytest skip 178 tests.
  Also skewing the 'Gain' time. I estimate it to account for 3 minutes,
  making the total gain ~20 minutes.
  Follow-up to 0455d8772a1af20ce63c46c5738582aa9b1b8441 #18509
  (It may be a better solution to disable libev for the local nghttp2
  build, to avoid this hidden dependency.)

- fix quiche jobs to use the local build of `libnghttp2`.

- stop installing the `clang` package for Windows-cross. `clang` and
  `clang-tidy` tools are preinstalled on the Ubuntu 24.04 runner.

Closes #18519