When searching for packages, rule out incompatible TTC versions

[mattpolzin]

Description

Prior to this change, the first package matching version requirements would be used by the compiler -- if that package was only installed with an incompatible TTC version, it simply cannot be used. After this change, we skip package directories with only incompatible TTC versions which allows the compiler to find a farther down option (if one exists) in some other directory that does have a compatible TTC vesrion.

For example, if you've got an incompatible package named foo at ~/.idris2/idris2-0.7.0/foo-0/12345 and a compatible package at ~/extra/idris2/foo-0/56789 this PR allows the compiler to succeed given ~/extra/idris2 is in IDRIS2_PACKAGE_PATH. Prior to this PR, that would not have worked.

When a package is passed over due to incompatible TTC version, you see the following warning:

Warning: Found version 0 of package pg-idris-tests installed with no compatible binaries for the current Idris2 compiler.

Reinstall pg-idris-tests with the current Idris2 compiler to resolve the issue.

• Add a test.

Should this change go in the CHANGELOG?

• If this is a fix, user-facing change, a compiler change, or a new paper
  implementation, I have updated CHANGELOG_NEXT.md (and potentially also
  CONTRIBUTORS.md).

[gallais]

This feels like it could have counter-intuitive results.
Any chance we can pre-emptively add a bit logging explaining the package selection strategy?
People can then turn it on if they want to see a rational for the behaviour they observe.

[mattpolzin]

Yeah logging is a good call. I wonder if this shouldn't even be a warning -- to have some packages only installed as incompatible binaries. Definitely already surprising prior to this PR to wonder why such a library simply isn't working.