capture riscv-arch-test repo tag in report

[Neel Gala]

Since the framework and tests are now in different repos, the RISCOF run report must also include the tag/version of the riscv-arch-test repo.

To achieve this, during the riscof run command, we will check

• if the suite directory is a git repo
• if the repo is indeed the riscv-arch-test repo
• There are no changes/pending commits to the repo
• then collect the tag that has been checked out.

If any of these checks fail, the report will indicate that a custom a suite was used to run the tests.