FE: Add support for group-level branch exceptions in Policy UI Editor

Why are we doing this work

In the scope of this issue, we would like to extend the current functionality to support branch_exceptions in group-level Policy Editor UI for both Scan Result and Scan Execution Policies.

Relevant links

• Epic
• Discussion about Design ( #425145 (comment 1589181780))
• Design Issue

Non-functional requirements

• Documentation: no documentation changes are needed until feature flag is enabled by default
• Feature flag: overall feature should be released behind feature flag security_policies_branch_exceptions, if FF is disabled we should not consider branch_exceptions when evaluating if policy is applicable,
• Performance:
• Testing:

Implementation plan

• MR1:
  • frontend ...

Verification steps

1. Create a new Group
2. Create a new Scan Result Policy in YAML mode and add branch_exceptions: ["dev", { full_path: "path/to/project", "name": "main" }]
3. Create a new Scan Execution Policy in YAML mode and add branch_exceptions: ["dev", { full_path: "path/to/project", "name": "main" }]
4. Go to Policies page and look how Policy Drawer is updated