[smpeg2] Cleanup, fix build, export config

[dg0yt]

Alternative to #32794.

• Changes comply with the maintainer guide
• SHA512s are updated for each updated download
• The "supports" clause reflects platforms that may be fixed by this new version
• Any fixed CI baseline entries are removed from that file.
• Any patches that are no longer applied are deleted from the port's directory.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is added to each modified port's versions file.

[MonicaLiu0311]

The usage test passed on x64-windows (header files found):

smpeg2 provides CMake targets:

    # this is heuristically generated, and may not be correct
    find_package(unofficial-smpeg2 CONFIG REQUIRED)
    target_link_libraries(main PRIVATE unofficial::smpeg2::smpeg2)