GHA: improve vcpkg cache, add BoringSSL ECH and LibreSSL MSVC jobs

GHA: improve vcpkg cache, add BoringSSL ECH and LibreSSL MSVC jobs

- cache on a per-package basis.
  Replace manual caching with a built-in solution. It shares cached
  package builds between jobs, e.g. libssh2 only builds once
  per platform (instead of once per job). Individual packages are built
  as needed (not the whole per-job tree). It also fixes the duplicate
  cache entry issues.
  Ref: https://learn.microsoft.com/en-us/vcpkg/consume/binary-caching-github-actions-cache
  Follow-up to e26cbe20cbedbea0ca743dd33880517309315cb2 #13979
  Follow-up to cb22cfca69bded45bf7f9c72c8e6764990490f11 #14077

- add BoringSSL job with ECH enabled. The first such job in the curl CI.

- add LibreSSL job.

- use vcpkg pre-installed on the runner image, instead of rolling our
  own. This is quicker, simpler and more robust.
  Follow-up to e26cbe20cbedbea0ca743dd33880517309315cb2 #13979

- show pre-installed vcpkg and ports version.

- drop `gsasl` dependency till it reaches the pre-installed vcpkg ports.

- re-add `find .` to see the binaries generated.

- simplify setting up `PATH`.

- exclude failing tests for any job enabling WinIDN.

- drop collecting and uploading log archives. We already dump CMake
  logs, and our build doesn't use Ninja. Rest of files weren't generated
  by the curl build. We don't aim to debug vcpkg package builds.

Closes #14090