Modernize docs using pydata_sphinx_theme [Screen recording 2025-12-22 4.54.40 PM.webm](https://github.com/user-attachments/assets/58b5254f-1357-4c09-9278-fb4763b5337d) Also visible in Dark mode. (default is auto based on system settings) <img width="2560" height="1440" alt="Screenshot 2025-12-22 5 01 55 PM" src="https://github.com/user-attachments/assets/f11e3705-d92c-4dfc-85d9-b09ae6a83661" /> Closes #41287 PiperOrigin-RevId: 857006550
buildgen: Template renderer for our build system.
distrib: Scripts to distribute language-specific packages and other distribution-related helper scripts.
dockerfile: Docker files to test gRPC.
doxygen: gRPC C/C++ documentation generation via Doxygen.
gce: Scripts to help setup testing infrastructure on GCE.
gcp: Helper scripts for interacting with various services on GCP (like Google container engine, BigQuery etc)
internal_ci: Support for running tests on an internal CI platform.
interop_matrix: Scripts to build, upload, and run gRPC clients in docker with various language/runtimes.
jenkins: Support for running tests on Jenkins.
run_tests: Scripts to run gRPC tests in parallel.
run_tests/performance: See the README for more notes on the performance tests.