CI: dump libcurl.pc (and curl-config) to log, verify .pc with pccritic tool

`pccritic` is available on the latest macOS runner revision (not every
job runs get it yet), Cygwin, MSYS2/mingw-w64 (one job, others will
follow on the next msys2/setup-msys2 Action bump). It will be
automatically used on BSDs, once they start offering it. Missing from
Linux jobs.

Also:
- GHA/windows: convert `libcurl.pc` to Unix newlines to bump score
  96 to 100 in mingw-w64 jobs.
  CMake-specific fix pending in: #22556
- GHA: verify with minimum `pccritic` score 94 to 100 (depending on CI
  job).
- build: fill `Maintainer:` `libcurl.pc` property when run curl CI.

Issues remaining:

macOS:
```
[info    ] Cflags adds an include path already on the default search path (pkgconf strips it): -I/usr/local/include (cflags/PC031)
[info    ] Libs adds a library path already on the default search path (pkgconf strips it): -L/usr/local/lib (libs/PC040)
[minor   ] Libs.private contains an unexpected flag: /Applications/Xcode_26.6.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX26.5.sdk/System/Library/Frameworks/GSS.framework (libs/PC041)
```

Windows:
```
[minor   ] file uses CRLF line endings (style/PC061)
```

Ref: #22556
Follow-up to b9254da617 #22548
Follow-up to 852f5d34da #22553
Follow-up to 4d9ba9fef4 #22545
Follow-up to 6c7993d4d9 #22536
Follow-up to 3f1c033afe #22519

Closes #22543

.github/workflows/http3-linux.yml

@@ -815,6 +815,12 @@ jobs:
           echo '::group::raw'; cat bld/lib/curl_config.h || true; echo '::endgroup::'
           grep -F '#define' bld/lib/curl_config.h | sort || true
 
+      - name: 'libcurl.pc, curl-config'
+        run: |
+          for f in libcurl.pc curl-config; do
+            echo "::group::${f}"; grep -v '^#' bld/"${f}" || true; echo '::endgroup::'
+          done
+
       - name: 'test configs'
         run: grep -H -v '^#' bld/tests/config bld/tests/http/config.ini || true