[infra] Add configuration for vm-tsan-mac-release-arm64.

Change-Id: I83e472910ed22394d9704afa48e24085fc65ebe4
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/447001
Reviewed-by: Alexander Aprelev <[email protected]>
Commit-Queue: Ryan Macnak <[email protected]>

Author: rmacnak-google

tools/bots/test_matrix.json

@@ -1394,10 +1394,11 @@
         "vm-asan-win-release-x64",
         "vm-msan-linux-release-x64",
         "vm-tsan-linux-release-x64",
+        "vm-tsan-mac-release-arm64",
         "vm-ubsan-linux-release-x64"
       ],
       "meta": {
-        "description": "This configuration is used by the X64 sanitizers."
+        "description": "This configuration is used by the sanitizers (high capacity machine pools)."
       },
       "steps": [
         {
@@ -1435,7 +1436,7 @@
         "vm-ubsan-linux-release-arm64"
       ],
       "meta": {
-        "description": "This configuration is used by the ARM64 sanitizers."
+        "description": "This configuration is used by the sanitizers (low capacity machine pools)."
       },
       "steps": [
         {