Build SQL dialect auto linter / add in github workflows

[keenzarate213]

Description & motivation

Adds a new CI check (sql_dialect_linter) that catches Databricks/Snowflake SQL
incompatibilities in the PR.

For each dialect, the workflow:

• Compiles every model and test in the edu_wh package against a dummy dbt
  profile and dummy macro overrides for anything that
  would require a database connection during compile (e.g. is_incremental,
  get_column_values, union_relations).
• Auto detects and excludes any model/test that still needs a warehouse
  connection to compile; currently
  bld_ef3__student_programs, bld_ef3__student_indicators,
  bld_ef3__student_assessments_long_results, and cfg_assessment_scores.
• Enables tpdm_warehouse and finance_warehouse, which are disabled by default, so
  they get checked linted as well.
• Lints the compiled SQL with sqlfluff and reports pass/fail counts split between
  models and tests.

Also added a check for known Databricks-incompatible function/type usage that
sqlfluff can't catch on its own since it only validates syntax, doesnt detect
a given function or type actually exists. Currently checks for
try_to_date() and casting as time, both valid syntax everywhere but with no
Databricks equivalent. I added a list directly in sql_dialect_linter.sh
(databricks_incompatible_patterns) so new ones are a one-line addition (we could also maybe store in a yaml?)

Versions (sqlfluff, dbt-core, dbt-databricks, dbt-snowflake) are pinned in
.github/workflows/requirements/sql-linter.txt.
Also had to add noqa: PRS (see documntation here) workaround (scoped to a single known macro) for an unsupported sqlfluff parsing gap around Databricks' variant_explode syntax,
and also allow for caching of virtualenv and dbt_packages in workflow so dependencies don't get
reinstalled/re-downloaded on every push in the branch.

Breaking changes introduced by this PR:

None, this is a new CI/tooling, no changes to warehouse models or logic.

PR Merge Priority:

• Low
• Medium
• High

Changes to existing files:

New files created:

• .github/scripts/sql_dialect_linter.sh: compiles + lints edu_wh against a dummy
  Databricks/Snowflake profile for the given dialect argument.
• .github/workflows/sql_dialect_linter.yml: runs the above on PRs for both dialects.
• .github/workflows/requirements/sql-linter.txt: pinned tool versions

Tests and QC done:

• Did a pressure test on a couple models, linter successfuly detected Databricks incompatibility (except for the try_to_date() function ~ which I had to add as a specific flag to error out because sqlfluff doesn't really check whether or not a function exist in a dialect

edu_wh PR Review Checklist:

Make sure the following have been completed before approving this PR:

• Description of changes has been added to Unreleased section of CHANGELOG.md. Add under ## New Features for features, etc.
• Code has been tested/checked for Databricks and Snowflake compatibility - EA engineers see Databricks checklist here
• Reviewer confirms the grain of all tables are unchanged, OR any changes are expected, communicated, and this PR is flagged as a breaking change (not for patch release)
• If a new configuration xwalk was added:
  • The code is written such that the xwalk is optional (preferred), and this behavior was tested, OR
  • The code is written such that the xwalk is required, and the required xwalk is added to edu_project_template, and this PR is flagged as breaking change (not for patch release)
  • A description for the new xwalk has been added to EDU documentation site here
• If a new configuration variable was added:
  • The code is written such that the variable is optional (preferred), and this behavior was tested, OR
  • The code is written such that the variable is required, and a default value was added to edu_project_template, and this PR is flagged as breaking change (not for patch release)
  • A description for the new variable has been added to EDU documentation site here