render to and to_columns on column and model level fk constraints

[MichelleArk]

resolves #271
docs dbt-labs/docs.getdbt.com/# - part of dbt-core issue

Core PR: dbt-labs/dbt-core#10414

Problem

As part of dbt-labs/dbt-core#8062. we are parsing and compiling new to and to_columns fields on ModelLevelConstraint and ColumnLevelConstraint.

Solution

dbt-adapters uses these new fields, when populated, to render out the foreign key constraint instead of expression. expression support remains as-is for backward-compatability.

Checklist

• I have read the contributing guide and understand what's expected of me
• I have run this code in development, and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• This PR has no interface changes (e.g. macros, cli, logs, json artifacts, config files, adapter interface, etc.) or this PR has already received feedback and approval from Product or DX

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[github-actions]

Thank you for your pull request! We could not find a changelog entry for this change. For details on how to document a change, see the contributing guide.

[MichelleArk]

Concrete Adapter Testing:

• Redshift: https://github.com/dbt-labs/dbt-redshift/actions/runs/10045111024?pr=880 ✅
• BigQuery: https://github.com/dbt-labs/dbt-bigquery/actions/runs/10045115685/job/27810428294?pr=1273 ✅
• Snowflake: https://github.com/dbt-labs/dbt-snowflake/actions/runs/10061145900/job/27810471129?pr=1143 ✅
• Spark: https://github.com/dbt-labs/dbt-spark/actions/runs/10045122646/job/27761711755?pr=1079 ✅
• Postgres: https://github.com/dbt-labs/dbt-postgres/actions/runs/10061120196 ✅