Drop support for bazel5; switch to all bzlmod. #4789

Job	Run time
VerifyFormatting	26s
x86_64 test	6m 34s
ClangTidy	50m 20s
arm64 test	6m 53s
KytheXrefs	0s
MacOsBuild	6m 24s
x86_64 test-clang	6m 22s
arm64 test-clang	6m 36s
PrepareVSPlugin	2m 2s
RunBantBuildCleaner	3m 18s
WindowsBuild	32m 4s
x86_64 test-nortti	6m 23s
x86_64 test-c++20	6m 32s
KytheVerification	0s
x86_64 test-c++23	6m 32s
x86_64 smoke-test	13m 50s
arm64 smoke-test	14m 38s
x86_64 asan	8m 15s
x86_64 asan-clang	7m 1s
x86_64 compile	6m 42s
arm64 compile	6m 7s
x86_64 compile-clang	5m 44s
arm64 compile-clang	5m 48s
x86_64 compile-static	5m 59s
arm64 compile-static	6m 3s
x86_64 compile-static-clang	5m 37s
arm64 compile-static-clang	6m 6s
x86_64 clean	7m 20s
arm64 clean	7m 8s
Build and deploy GitHub pages	6s
📦 Release	0s
	4h 6m 50s

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