Partially disable rule mode on parsing error for pipeline execution policies

Why are we doing this work

Currently when there is a yaml parsing error, the entire rule mode disables, which could be overkill (e.g. if the parsing error is because of a rule, then the action section should not have to be disabled)

Relevant links

Non-functional requirements

• Documentation:
• Feature flag:
• Performance:
• Testing:

Implementation plan

• frontend implement for pipeline execution policy
  • similar to Update scan execution rule mode errors (!166102 - merged)

Verification steps

1. Upload a GitLab Ultimate license
2. Navigate to a project => Secure => Policies => New policy => Pipeline execution policy
3. Navigate to yaml mode and mess around with the yaml
4. Navigate to rule mode and see that only part of it is disabled