Add scan execution policies to the policy list

What does this MR do?

The policy list now also fetches scan execution policies and displays them along with network policies. This also renames a few things to better reflect the fact that we no longer display network policies only. The specs have been reorganized and cleaned up to make sure we only test relevant things, that no test-cases are duplicated, and that we only create a single wrapper per test case. We also now mount shallow wrappers when a full mount isn't necessary.

How to test this?

Since it is not yet possible to create scan execution policies, the easiest way to test this would be to mock one client-side:

diff --git a/ee/app/assets/javascripts/threat_monitoring/graphql/queries/scan_execution_policies.query.graphql b/ee/app/assets/javascripts/threat_monitoring/graphql/queries/scan_execution_policies.query.graphql
index 0b9a2e08e8a..9c3ba33ddf6 100644
--- a/ee/app/assets/javascripts/threat_monitoring/graphql/queries/scan_execution_policies.query.graphql
+++ b/ee/app/assets/javascripts/threat_monitoring/graphql/queries/scan_execution_policies.query.graphql
@@ -1,5 +1,5 @@
 query scanExecutionPolicies($fullPath: ID!) {
-  project(fullPath: $fullPath) {
+  project(fullPath: $fullPath) @client {
     scanExecutionPolicies {
       nodes {
         name
diff --git a/ee/app/assets/javascripts/threat_monitoring/index.js b/ee/app/assets/javascripts/threat_monitoring/index.js
index c2f007379e2..843980468f6 100644
--- a/ee/app/assets/javascripts/threat_monitoring/index.js
+++ b/ee/app/assets/javascripts/threat_monitoring/index.js
@@ -9,7 +9,27 @@ Vue.use(VueApollo);
 
 const apolloProvider = new VueApollo({
   defaultClient: createDefaultClient(
-    {},
+    {
+      Query: {
+        project: () => {
+          return {
+            __typename: 'Project',
+            scanExecutionPolicies: {
+              __typename: 'ScanExecutionPolicyConnection',
+              nodes: [
+                {
+                  __typename: 'ScanExecutionPolicy',
+                  name: 'Scan execution policy',
+                  yaml: 'some yaml',
+                  enabled: true,
+                  updatedAt: new Date(),
+                },
+              ],
+            },
+          };
+        },
+      },
+    },
     {
       assumeImmutableResults: true,
       cacheConfig: {

Screenshots (strongly suggested)

Before	After

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

Does this MR contain changes to processing or storing of credentials or tokens, authorization and authentication methods or other items described in the security review guidelines? If not, then delete this Security section.

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Related to #333727 (closed)