USD github workflows updates:

- Trigger workflows on pull requests
- Add Validation job to filter PR files to prevent triggering workflows for files that span the workflows directory
- Remove GetGitRef job and use github.ref instead
- Remove GetUser job
- Remove /AzurePipelines run comment trigger

(Internal change: 2367224)

Author: shahbazk8194

.github/workflows/buildusd.yml

@@ -5,49 +5,35 @@ on:
     branches:
       - dev
       - release
-  issue_comment:
-    types: [created]
+  pull_request:
+    branches:
+      - dev
+    paths:
+      - '**'
+      - '!.github/workflows/**'
 
 jobs:
-  GetUser:
+  Validation:
     runs-on: ubuntu-22.04
-    timeout-minutes: 5
+    timeout-minutes: 30
     outputs:
-      require-result: ${{ steps.check.outputs.require-result }}
+      validation-failed: ${{ steps.changed-workflows.outputs.any_changed }}
     steps:
-      - uses: actions-cool/check-user-permission@v2
-        id: check
+      - name: Checkout code
+        uses: actions/checkout@v4
         with:
-          require: 'write'
-          username: ${{ github.event.comment.user.login }}
-
-  GetGitRef:
-    runs-on: ubuntu-22.04
-    timeout-minutes: 5
-    outputs:
-      ref: ${{ steps.setter.outputs.ref }}
-    steps:
-      - name: Get push ref
-        if: ${{ github.event_name == 'push' }}
-        run: |
-          echo "REF=${{ github.ref }}" >> $GITHUB_ENV
-      - name: Get PR ref
-        if: ${{ github.event.issue.pull_request }}
-        run: |
-          echo "REF=refs/pull/${{ github.event.issue.number }}/merge" >> $GITHUB_ENV
-      - name: Print ENV_VAR
-        run: |
-          echo "The value of REF is $REF"
-      - name: Set ENV_VAR
-        id: setter
-        run: |
-          echo "ref=$REF" >> "$GITHUB_OUTPUT"
+          ref: ${{ github.ref }}
+      - name: Check workflows directory
+        id: changed-workflows
+        uses: tj-actions/changed-files@ed68ef82c095e0d48ec87eccea555d944a631a4c #v46
+        with:
+          files: |
+            .github/workflows/**
 
   Linux:
     needs:
-      - GetUser
-      - GetGitRef
-    if: ${{ (github.event.issue.pull_request && contains(github.event.comment.body, '/AzurePipelines run') && needs.GetUser.outputs.require-result == 'true' ) || github.event_name == 'push' }}
+      - Validation
+    if: ${{ (github.event_name == 'pull_request' && needs.Validation.outputs.validation-failed != 'true') || github.event_name == 'push' }}
     runs-on: ubuntu-22.04
     env:
       PYTHON_VERSION: "3.9"
@@ -56,7 +42,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
-          ref: ${{needs.GetGitRef.outputs.ref}}
+          ref: ${{ github.ref }}
       - name: Restore cached artifacts
         id: cache-usd-build-dependency
         uses: actions/cache/restore@v4
@@ -98,9 +84,8 @@ jobs:
 
   macOS:
     needs:
-      - GetUser
-      - GetGitRef
-    if: ${{ (github.event.issue.pull_request && contains(github.event.comment.body, '/AzurePipelines run') && needs.GetUser.outputs.require-result == 'true' ) || github.event_name == 'push' }}
+      - Validation
+    if: ${{ (github.event_name == 'pull_request' && needs.Validation.outputs.validation-failed != 'true') || github.event_name == 'push' }}
     runs-on: macos-13
     env:
       PYTHON_VERSION: "3.11"
@@ -109,7 +94,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
-          ref: ${{needs.GetGitRef.outputs.ref}}
+          ref: ${{ github.ref }}
       - name: Restore cached artifacts
         id: cache-usd-build-dependency
         uses: actions/cache/restore@v4
@@ -156,9 +141,8 @@ jobs:
 
   Windows:
     needs:
-      - GetUser
-      - GetGitRef
-    if: ${{ (github.event.issue.pull_request && contains(github.event.comment.body, '/AzurePipelines run') && needs.GetUser.outputs.require-result == 'true' ) || github.event_name == 'push' }}
+      - Validation
+    if: ${{ (github.event_name == 'pull_request' && needs.Validation.outputs.validation-failed != 'true') || github.event_name == 'push' }}
     runs-on: windows-2019
     env:
       PYTHON_VERSION: "3.9"
@@ -167,7 +151,7 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
         with:
-          ref: ${{needs.GetGitRef.outputs.ref}}
+          ref: ${{ github.ref }}
       - name: Restore cached artifacts
         id: cache-usd-build-dependency
         uses: actions/cache/restore@v4