Add policy type column

What does this MR do?

• Add the sortable policy type column.
• Make the updatedAt column sortable.
• Set default sort to updateAt desc.

How to test this?

Since it's not yet possible to create scan execution policies, you'll need to mock some client-side. You can do that by applying the following patch:

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 83e39a6355b..5eeb6b08b42 100644
--- a/ee/app/assets/javascripts/threat_monitoring/index.js
+++ b/ee/app/assets/javascripts/threat_monitoring/index.js
@@ -9,7 +9,34 @@ 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: '2021-06-18T18:25:42Z',
+                },
+                {
+                  __typename: 'ScanExecutionPolicy',
+                  name: 'Execute DAST scan',
+                  yaml: 'some yaml',
+                  enabled: false,
+                  updatedAt: '2021-06-20T18:25:42Z',
+                },
+              ],
+            },
+          };
+        },
+      },
+    },
     {
       assumeImmutableResults: true,
       cacheConfig: {

Screenshots (strongly suggested)

Note: the screenshots below were captured before !64959 (merged) was merged, so the Status column still uses the old design.

Before

After

Context	Screenshot
Default sort
Sort by update date ascending
Sort by policy type descending
Sort by policy type ascending

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 #273781 (closed)