This PR removes all of the custom version parsing functions where we try
to make sense about the version (e.g. extracting major/minor versions).

Whilst doing this I actually think that I made it easier to support
bazel-contrib#2837.

…el-contrib#2969)

Add latest toolchain builds and attempt adding a beta build.

This shows/tests that we can handle pre-release versions just fine
and we are able to test the toolchain matching. Whilst at it it
implements
the static advertising of the remaining interpreter information.

Fixes bazel-contrib#2837

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Co-authored-by: Richard Levasseur <richardlev@gmail.com>