Adding new (external) test suites to IREE

[Scott Todd]

Hi all,

I've been setting up some new test suite infrastructure that is just about ready for use.

• More background is on the tracking issue: https://github.com/openxla/iree/issues/16372
• The external test suite itself has gone through some review at https://github.com/nod-ai/SHARK-TestSuite/pull/68 and https://github.com/nod-ai/SHARK-TestSuite/pull/75 
  
• The IREE integration of the test suite is up at https://github.com/openxla/iree/pull/16589

I'm anticipating some churn as the test suite is put into use. I'll be keeping an eye on each of these areas:

• Test cases newly failing or passing
• Test cases needing to be regenerated after [Torch]MLIR updates
  
• CI builds failing in ways that need infrastructure debugging

If anyone has feedback about the overall setup or would like to help contribute new test cases, please feel free to reach out.

Thanks,

Scott