Feature: add group by

[xtutran]

Description & motivation

Hi there,

I would like to group the data in profiler. I am not so sure if this feature is useful for everyone. But this is something I would like to have for my own usage. Feel free to discard the PR if you think it not so useful.

Cheers, Tran

Checklist

• [x] I have verified that these changes work locally on the following warehouses (Note: it's okay if you do not have access to all warehouses, this helps us understand what has been covered):
  • [x] Postgres
  • [x] BigQuery
  • [ ] Snowflake
  • [ ] Redshift
  • [ ] SQL Server
  • [ ] Databricks
• [x] I have written tests for new macros (either as dbt schema tests in integration_tests/models, dbt data tests in integration_tests/tests or integration tests in the CI workflow)
• [x] I have updated the README.md (if applicable)

[stumelius]

@xtutran This had completely went by my radar, sorry for that. I'll merge this as is but I'll make minor change to the group_by argument so that it's a list of column names. I'll open a separate PR for that.

Thanks for your contribution :)