Removes the test category annotation and renames the assertions

[alancai98]

Closes https://github.com/partiql/partiql-tests/issues/16 and addresses PR comments from #15.

This PR attempts to improve the ergonomics of defining partiql-tests data through the following changes:

• Renames parse -> syntax in directories, assertions, and ISL schema
• Renames semantic -> static-analysis in directories, assertions, and ISL schema
• Renames directory pass -> success to better align with the renamed assertions
• Removes the repetitive test category annotation for test cases
• Updates the ISL and documentation following the above changes
• Moves some is-operator tests from the syntax error category to static-analysis error category

Following these changes, the corresponding test runner parse code in partiql-lang-rust will need updated.

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