Fix yaml schema validation for scan result policy

What does this MR do and why?

Fix yaml schema validation for scan result policy

• the name of the scan result policy was updated to approval policy
• to allow for both names to work, the properties were moved into a shared reference (Add support for approval_settings and any_merge... (!130189 - merged))
• update frontend to find properties in that shared reference
• update frontend to fail gracefully for policies that are not in the schema
• update tests to be more robust

Changelog: fixed

EE: true

MR acceptance checklist

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license
2. Apply the following patch

Patch

diff --git a/app/assets/javascripts/editor/extensions/source_editor_security_policy_schema_ext.js b/app/assets/javascripts/editor/extensions/source_editor_security_policy_schema_ext.js
index 1647b0ec457c..684f9ef07dd9 100644
--- a/app/assets/javascripts/editor/extensions/source_editor_security_policy_schema_ext.js
+++ b/app/assets/javascripts/editor/extensions/source_editor_security_policy_schema_ext.js
@@ -63,6 +63,7 @@ export class SecurityPolicySchemaExtension {
         });
         const modelFileName = instance.getModel().uri.path.split('/').pop();
 
+        console.log(singlePolicySchema);
         registerSchema({
           uri: getSecurityPolicySchemaUrl({ namespacePath, namespaceType }),
           schema: singlePolicySchema,

2. Navigate to a project => Secure => Policies => New policy
3. Select Scan Execution policy => Open the developer console ( CMD + OPTION + k )
4. Navigate to yaml mode
5. Ignore the errors; they will be addressed in Security Policy yaml validation does not work w... (#461252 - closed).
6. Verify the console log has the properties value
7. Navigate back to the selector page => Select Merge request approval policy => Open the developer console ( CMD + OPTION + k )
8. Navigate to yaml mode
9. Ignore the errors; they will be addressed in Security Policy yaml validation does not work w... (#461252 - closed).
10. Verify the console log has the properties value

Related to #457789 (closed)