Move coverage to its own workflow (#1063)

The coverage job does not support sharding and takes ~1h to run. That's
~40 minutes longer than all other linux test runs. By breaking out
coverage from the linux workflow we can get unit test results from
datadog in less than half the time.

b/290997541

.github/workflows/coverage.yaml

@@ -0,0 +1,30 @@
+name: coverage
+
+on:
+  pull_request:
+    types:
+      - opened
+      - edited
+      - reopened
+      - synchronize
+  push:
+    branches:
+      - main
+      - feature/*
+
+jobs:
+  linux-coverage:
+    # TODO(b/286302961): Move back and re-enable this check once sharding is supported.
+    # Run on main branch for pushes, PRs and manual invocations.
+    # if: |
+    #  ${{ github.ref == 'refs/heads/main' &&
+    #      (github.event_name == 'push' ||
+    #      github.event_name == 'pull_request' ||
+    #      (github.event_name == 'workflow_dispatch' && inputs.nightly == 'false')) }}
+    uses: ./.github/workflows/main.yaml
+    permissions:
+      packages: write
+      pull-requests: write
+    with:
+      platform: linux-coverage
+      nightly: ${{ github.event.inputs.nightly }}

.github/workflows/linux.yaml

@@ -56,17 +56,3 @@ jobs:
       platform: linux-modular
       nightly: ${{ github.event.inputs.nightly }}
       modular: true
-  linux-coverage:
-    # Run on main branch for pushes, PRs and manual invocations.
-    if: |
-     ${{ github.ref == 'refs/heads/main' &&
-         (github.event_name == 'push' ||
-         github.event_name == 'pull_request' ||
-         (github.event_name == 'workflow_dispatch' && inputs.nightly == 'false')) }}
-    uses: ./.github/workflows/main.yaml
-    permissions:
-      packages: write
-      pull-requests: write
-    with:
-      platform: linux-coverage
-      nightly: ${{ github.event.inputs.nightly }}