Change `scan_execution_policies_action_limit` application setting behaviour to opt-in

Why are we doing this work

We need to make the behaviour of the scan_execution_policies_action_limit application setting opt-in:

• change the default limit of the scan_execution_policies_action_limit application setting to 0 from currently 10
• update backend and frontend so that the value 0 disables enforcement of the limit
• (for simplicity) remove the feature flags, since the default value of 0 already disables the limit

Relevant links

• &14460 (comment 2438493756)
• &14460

Non-functional requirements

• Documentation:
• Feature flag: Remove the existing feature flag since the application setting will default to 0 which effectively disables it
• Performance:
• Testing:

Implementation plan

n/a

Verification steps

n/a