Closes #26615 Add nimbus configuration feature flags for MR 2022

.experimenter.yaml

@@ -44,6 +44,14 @@ messaging:
     triggers:
       type: json
       description: "A collection of out the box trigger expressions. Each entry maps to a valid JEXL expression.\n"
+mr2022:
+  description: Features for MR 2022.
+  hasExposure: true
+  exposureDescription: ""
+  variables:
+    sections-enabled:
+      type: json
+      description: This property provides a lookup table of whether or not the given section should be enabled.
 nimbus-validation:
   description: A feature that does not correspond to an application feature suitable for showing that Nimbus is working. This should never be used in production.
   hasExposure: true

nimbus.fml.yaml

@@ -216,6 +216,35 @@ features:
             EXPIRES_QUICKLY:
               priority: 100
               max-display-count: 1
+  mr2022:
+    description: Features for MR 2022.
+    variables:
+      sections-enabled:
+        description: "This property provides a lookup table of whether or not the given section should be enabled."
+        type: Map<MR2022Section, Boolean>
+        default:
+          {
+            "home-onboarding-dialog-new-users": false,
+            "home-onboarding-dialog-existing-users": false,
+            "sync-cfr": false,
+            "wallpapers-selection-tool": false,
+            "jump-back-in-cfr": false,
+            "tcp-cfr": false,
+            "tcp-feature": false
+          }
+    defaults:
+      - channel: developer
+        value: {
+          "sections-enabled": {
+            "home-onboarding-dialog-new-users": true,
+            "home-onboarding-dialog-existing-users": true,
+            "sync-cfr": true,
+            "wallpapers-selection-tool": true,
+            "jump-back-in-cfr": true,
+            "tcp-cfr": true,
+            "tcp-feature": true
+          }
+        }
 
   unified-search:
     description: A feature allowing user to easily search for specified results directly in the search bar.
@@ -351,3 +380,20 @@ types:
           description: Jump back in onboarding CFR.
         first-run-onboarding:
           description: First run onboarding page updates.
+    MR2022Section:
+      description: The identifiers for the sections of the MR 2022.
+      variants:
+        home-onboarding-dialog-existing-users:
+          description: Home onboarding dialog for upgraded users.
+        home-onboarding-dialog-new-users:
+          description: Home onboarding dialog for new users.
+        sync-cfr:
+          description: CFR for the first time you see a synced tab on the home screen.
+        wallpapers-selection-tool:
+          description: Wallpapers selection dialog tool for the home screen.
+        jump-back-in-cfr:
+          description: Jump back-in onboarding message.
+        tcp-cfr:
+          description: CFR for the first time you use the browse with Total Cookie Protection on the browser screen.
+        tcp-feature:
+          description: Controls the Total Cookie Protection feature.