Started adding tests. Will try to cover code that would add value.

/claim #560

Please go through the following checklist

• The PR title and commit messages adhere to guidelines here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/CONTRIBUTING.md. In particular ! is used if and only if at least one breaking change has been introduced.
• I have run the ci check script with source scripts/run_ci_checks.sh.
• I have run the clean commit check script with source scripts/check_commits.sh, and the commit history is certified to follow clean commit guidelines as described here: https://github.com/spaceandtimelabs/sxt-proof-of-sql/blob/main/COMMIT_GUIDELINES.md
• The latest changes from main have been incorporated to this PR by simple rebase if possible, if not, then conflicts are resolved appropriately.

Rationale for this change

Gradually increasing test coverage

What changes are included in this PR?

Added new tests

proof-of-sql-parser/src/posql_time/timezone.rs
proof-of-sql-parser/src/posql_time/timestamp.rs
proof-of-sql-parser/src/identifier.rs
proof-of-sql-parser/src/intermediate_ast.rs

Additionally, added check for time zone boundaries, hours should not be over 12, and minutes should not be over 60 (please correct me if I am doing it wrong). This change is also tested

Ignoring

Ignored because some tests felt redundant, I am open for suggestions.

proof-of-sql/src/base/arrow/owned_and_arrow_conversions.rs
proof-of-sql/src/base/arrow/column_arrow_conversions.rs
proof-of-sql/src/base/database/column_repetition_operation.rs

Are these changes tested?

Yes.