Removes ISL and PIG

[johnedquinn]

Relevant Issues

• Dumps partiql-lang evaluation and parsing test cases and removes partiql-lang source #1593

Description

• Once Dumps partiql-lang evaluation and parsing test cases and removes partiql-lang source #1593 is merged, I can rebase and mark as ready for review.
• This removes ISL and PIG. It also adds the API check for visibility modifiers for partiql-ast.

License Information

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

PR feedback has been addressed