Allow portfile.cmake to get information defined in CONTROL file

[tobbi]

It would be great to get the version or other things defined in the CONTROL file to use as a reference to vcpkg_from_github.

Best would be something to get the major, minor and patch version number using vcpkg functions or variables.

[LilyWangL]

https://github.com/microsoft/vcpkg/blob/master/docs/maintainers/control-files.md

[isanych]

Side effect of this PR - #7129 - versions (and other info from control) are exposed in cmake