chore(ci): Remove conditional integration testing (#12591)

We instrumented conditional execution of some of our flakier integration test
suites: viz, multicluster, and policy. Since then, we have introduced retries
that ameliorate flakiness. The current state allows these tests to regress on
main, to be discovered only at release time.

This commit removes the conditional execution of these tests, and instead
runs all integration tests uniformly.

.github/workflows/integration.yml

@@ -45,60 +45,9 @@ jobs:
             .devcontainer/**
             **/Chart.yaml
             **/README*
-      - uses: tj-actions/changed-files@0874344d6ebbaa00a27da73276ae7162fadcaf69
-        id: policy
-        with:
-          files: |
-            .github/workflows/integration.yml
-            .proxy-version
-            Cargo.lock
-            charts/linkerd-control-plane/**
-            charts/linkerd-crds/templates/policy/**
-            justfile
-            policy-controller/**
-            policy-test/**
-            rust-toolchain.toml
-          files_ignore: |
-            **/Chart.yaml
-            **/README*
-      - uses: tj-actions/changed-files@0874344d6ebbaa00a27da73276ae7162fadcaf69
-        id: multicluster
-        with:
-          files: |
-            .github/workflows/integration.yml
-            .proxy-version
-            justfile
-            multicluster/**
-            test/integration/multicluster/**
-          files_ignore: |
-            **/Chart.yaml
-            **/README*
-      - uses: tj-actions/changed-files@0874344d6ebbaa00a27da73276ae7162fadcaf69
-        id: viz
-        with:
-          files: |
-            .github/workflows/integration.yml
-            .proxy-version
-            justfile
-            viz/**
-            test/integration/viz/**
-            bin/_test-helper.sh
-          files_ignore: |
-            **/Chart.yaml
-            **/README*
     outputs:
       tag: ${{ steps.tag.outputs.tag }}
-      changed-core: ${{ steps.core.outputs.any_changed }}
-      changed-policy: ${{ steps.policy.outputs.any_changed }}
-      changed-multicluster: ${{ steps.multicluster.outputs.any_changed }}
-      changed-viz: ${{ steps.viz.outputs.any_changed }}
-      changed: >-
-        ${{
-          steps.core.outputs.any_changed == 'true' ||
-          steps.policy.outputs.any_changed == 'true' ||
-          steps.multicluster.outputs.any_changed == 'true' ||
-          steps.viz.outputs.any_changed == 'true'
-        }}
+      changed: ${{ steps.core.outputs.any_changed }}
 
   info:
     needs: meta
@@ -109,10 +58,6 @@ jobs:
         run: |
           echo "tag=${{ needs.meta.outputs.tag }}"
           echo "changed=${{ needs.meta.outputs.changed }}"
-          echo "changed-core=${{ needs.meta.outputs.changed-core }}"
-          echo "changed-policy=${{ needs.meta.outputs.changed-policy }}"
-          echo "changed-multicluster=${{ needs.meta.outputs.changed-multicluster }}"
-          echo "changed-viz=${{ needs.meta.outputs.changed-viz }}"
 
   build-cli:
     needs: meta
@@ -211,7 +156,7 @@ jobs:
 
   test-policy:
     needs: [meta, build-cli, build-core]
-    if: needs.meta.outputs.changed-policy == 'true'
+    if: needs.meta.outputs.changed == 'true'
     runs-on: ubuntu-22.04
     timeout-minutes: 20
     strategy:
@@ -337,7 +282,7 @@ jobs:
 
   test-viz:
     needs: [meta, build-cli, build-core, build-ext]
-    if: needs.meta.outputs.changed-viz == 'true'
+    if: needs.meta.outputs.changed == 'true'
     runs-on: ubuntu-22.04
     timeout-minutes: 15
     steps:
@@ -363,7 +308,7 @@ jobs:
 
   test-multicluster:
     needs: [meta, build-cli, build-core, build-ext]
-    if: needs.meta.outputs.changed-multicluster == 'true'
+    if: needs.meta.outputs.changed == 'true'
     runs-on: ubuntu-22.04
     timeout-minutes: 20
     strategy: