add tests for rendering foreign key and unique constraints

[MichelleArk]

Updates tests for core PR: dbt-labs/dbt-core#7512

resolves dbt-labs/dbt-core#7417

Description

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• 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
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[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 dbt-snowflake contributing guide.

[github-actions]

The backport to 1.5.latest failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-1.5.latest 1.5.latest
# Navigate to the new working tree
cd .worktrees/backport-1.5.latest
# Create a new branch
git switch --create backport-596-to-1.5.latest
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 efe2eba0b45d0549576831c366e3815b899a7d3a
# Push it to GitHub
git push --set-upstream origin backport-596-to-1.5.latest
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-1.5.latest

Then, create a pull request where the base branch is 1.5.latest and the compare/head branch is backport-596-to-1.5.latest.