FE: Add merge request option selector in rules of scan result policy

Why are we doing this work

We are adding any merge request option for rules section in scan result policy

Now we only have 2 options security scan and license scan.

This issue adds third option

Relevant links

• See epic for more information

Design

Current design doesn't include branch exceptions. It will be right after any branches dropdown

Non-functional requirements

• Documentation:
• Testing:

Implementation plan

• frontend Create new component similar to security_scan_rule_builder.vue and license_scan_rule_builder.vue
• frontend Update scan_result_policy/base_layout/scan_type_select.vue to have third new option Any merge request
• frontend Add new rule type in policy_editor/scan_result_policy/lib/rules.js and update getDefaultRule

Verification steps

1. Upload a GitLab Ultimate license
2. Navigate to a project => Security & Compliance => Policies => New policy => Scan result Policy
3. Select Any merge request option in rules section
4. Make sure yaml is updated correctly
5. Switch between modes, make sure selected rule option stays selected
6. Verify same flow for editing existing scan result policy
   1. Scan result Policy