Merge pull request #9274 from ctiller/modulenotes

src/core/ext/README.md

src/core/ext/resolver/README.md

src/core/ext/transport/README.md

src/core/ext/transport/chttp2/README.md

src/core/lib/README.md

src/core/lib/channel/README.md

src/core/lib/iomgr/README.md

src/core/lib/surface/README.md

src/core/lib/transport/README.md

src/core/lib/tsi/README.md

templates/tools/doxygen/Doxyfile.include

tools/doxygen/Doxyfile.c++.internal

tools/doxygen/Doxyfile.core.internal