Proposal: move disable-locking flag to digger.yml

[motatoes]

Currently we have disable locking in action.yml and it was working fine for both backendless and orchestrator modes.

However we recently moved orchestrator locking to be in database for performance reasons (#1524) .

Now we have introduced another issue because there is no longer a way to disable locking if you are using digger with orchestrator mode (the flag was only avaiable in cli and since with orchestrator locking no longer performed in the cli it means that you can no longer disable locking by passing disable-locking to the action directly.

Propose to move that flag to a top level digger.yml value since then both orchestrator and cli can read it unified and have consistent behaviour:

# digger.yml

disable_locking: true

projects:
    - name: balbla
      dir: bla

Then the backend can pick this up in the webhook and if set then we don't perform any locking checks. Also we deprecate the older disable-locking from the action and rely on digger.yml to perform this locking disabling moving forward

[motatoes]

This is now done using a flag called pr_locks: false instead of disable_locking: true

https://docs.digger.dev/howto/disable-locking