Run ODT jobs on dedicated runners (#2079)

Make on-device test jobs run on dedicated runners that use very little
CPU and RAM. This should free up linux runners and reduce job queueing.

b/298255792

.github/workflows/main.yaml

@@ -139,7 +139,7 @@ jobs:
   # Builds, tags, and pushes Cobalt docker build images to ghr.
   docker-build-image:
     needs: [initialize]
-    runs-on: [self-hosted, linux, X64]
+    runs-on: [self-hosted, linux-runner]
     permissions:
       packages: write
     steps:
@@ -177,7 +177,7 @@ jobs:
     needs: [initialize]
     permissions:
       packages: write
-    runs-on: [self-hosted, linux, X64]
+    runs-on: [self-hosted, linux-runner]
     steps:
       - name: Checkout files
         uses: kaidokert/[email protected]
@@ -211,7 +211,7 @@ jobs:
   build:
     needs: [initialize, docker-build-image]
     permissions: {}
-    runs-on: [self-hosted, linux, X64]
+    runs-on: [self-hosted, linux-runner]
     name: ${{matrix.name}}_${{matrix.config}}
     strategy:
       fail-fast: false
@@ -298,7 +298,7 @@ jobs:
             inputs.nightly == 'true' || github.event_name == 'schedule') &&
             vars.RUN_ODT_TESTS_ON_NIGHTLY != 'False') ||
           ( github.event_name == 'push' && vars.RUN_ODT_TESTS_ON_POSTSUBMIT != 'False' ) )
-    runs-on: [self-hosted, linux, X64]
+    runs-on: [self-hosted, odt-runner]
     name: ${{ matrix.name }}_on_device_${{ matrix.shard }}
     container: ${{ needs.docker-unittest-image.outputs.docker_unittest_tag }}
     permissions: {}
@@ -328,7 +328,7 @@ jobs:
     needs: [initialize, docker-unittest-image, build]
     permissions: {}
     if: needs.initialize.outputs.on_host_test == 'true'
-    runs-on: [self-hosted, linux, X64]
+    runs-on: [self-hosted, linux-runner]
     name: ${{matrix.name}}_${{matrix.shard}}_test
     strategy:
       fail-fast: false