[graphviz,librsvg,libcroco] Refresh

[dg0yt]

graphviz

Properly cleanup and refresh patches. Amends #33795. Fixes #33926 which actually is my #33855 (comment) and which delayed feedback on #33795.

libcroco, librsvg

Revise dependencies.
Consistent use of pkgconfig for import and export. I see no benefit from unofficial exported CMake config when it relies on pkgconfig for imported dependencies.

libcroco: Use official (upstream) header installation dir. Install pc file. Drop unofficial debug postfix.
librsvg: Use official pc file name. Always build pixbufloader-svg as module (DLL), and install it to official location (#8015 (comment)).

[talregev]

Add an empty comment that will restart the tests and not hangout on license/cla.

[JonLiu1993]

Tested usage successfully by librsvg:x64-windows:

librsvg can be imported via CMake FindPkgConfig module:

    find_package(PkgConfig REQUIRED)
    pkg_check_modules(LIBRSVG librsvg-2.0 IMPORTED_TARGET REQUIRED)
    target_link_libraries(main PRIVATE PkgConfig::LIBRSVG)

libcroco:x64-windows:

    find_package(PkgConfig REQUIRED)
    pkg_check_modules(LIBCROCO libcroco-0.6 IMPORTED_TARGET REQUIRED)
    target_link_libraries(main PRIVATE PkgConfig::LIBCROCO)