.github; experiment with self-hosted env for milvus itests

Author: mohamedawnallah

.github/workflows/milvus_integration_tests.yml

@@ -14,7 +14,7 @@ on:
 jobs:
   milvus-tests:
     name: ${{ matrix.job_name }} (${{ matrix.job_phrase }} ${{ matrix.python_version }})
-    runs-on: ubuntu-latest
+    runs-on: [self-hosted, ubuntu-20.04, highmem22]
     timeout-minutes: 240
     strategy:
       fail-fast: false