[Flags] Switch default of behavior change flag source_freshness_run_project_hooks + add deprecation for old value

[jtcohen6]

Housekeeping

• I am a maintainer of dbt-core

Short description

Follow-up to #9366 + #10063

In dbt-core v1.9, we will be changing the default of source_freshness_run_project_hooks from False to True.

Acceptance criteria

• Default value of source_freshness_run_project_hooks project-only flag is True instead of False

Suggested Tests

• TestHooksInSourceFreshness: hooks should run as part of source freshness, without any explicitly setting of source_freshness_run_project_hooks flag in dbt_project.yml
• Deprecation warning: https://github.com/dbt-labs/dbt-core/blob/7df747ae04a8c99dbd745085f42cd4647ec71d80/tests/functional/deprecations/test_deprecations.py`

Impact to Other Teams

no impact

Will backports be required?

no backports

Context

https://docs.getdbt.com/reference/global-configs/behavior-changes

[jtcohen6]

@MichelleArk @martynydbt I changed the milestone of this issue from v1.8 → v1.9, and I've updated the description of the issue accordingly. We need to get a few more customer comms pieces in place before we're ready to go through the full behavior change lifecycle.