feat(FIR-42592): allow agg index without key columns

[ptiurin]

Description

Aggregation index SQL no longer requires key columns to be present as a part of it. Reflecting this change in dbt compiler.

Checklist

• 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 run changie new and committed everything in .changes folder
• I have removed any print or log calls that were added for debugging.
• I have verified that this PR contains only code changes relevant to this PR.
• If further integration tests are now passing I've edited tests/functional/adapter/* to account for this.
• I have pulled/merged from the main branch if there are merge conflicts.
• After pulling/merging main I have run pytest on the included or updated tests/functional/adapter/.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud