* upgrade ruby docker images to debian 11
* upgrade C# docker images to debian11
* update sanity dockerimage to debian11
* upgrade cxx interop to debian11
* add ccache to python interop images
* enable use of ccache for interop tests
* adjust run_tests.py to new docker images
* add ccache to rake-compiler-dock docker images
* improve prepare_ccache_symlinks_rc
* enable use of ccache in rake-compiler-dock docker containers
* add ccache support for python_manylinux2014_aarch64
* add ccache support for python_linux_armv7
* deduplicate python3.9 install
* ccache for crosscompiled darwin gems is broken
* fix bash -l resetting of PATH in grpc_artifact_python_linux_armv7
* support "move and respawn" for kokoro jobs
* delete_nonartifacts.sh no longer needed
* bazel distribtest dont publish any artifacts
* try the altsrc respawn for selected jobs
* use altsrc for all windows CI jobs
* use altsrc for all macos CI jobs
* only move files under src/github
* fix uploading artifacts on windows
The source code is moved from src/python to
src/python/src. A setup.py is added at
src/python. The build_python.sh and
run_python.sh scripts are updated to build
and run the Python tests by building a
package and installing it in the developer's
Python 2.7 virtual environment.