Drop support for bazel5; switch to all bzlmod. #4791

Job	Run time
ClangTidy	1h 30m 9s
RunBantBuildCleaner	3m 22s
x86_64 test	3m 55s
KytheVerification	0s
arm64 test	4m 10s
KytheXrefs	0s
x86_64 test-clang	3m 50s
MacOsBuild	4m 2s
arm64 test-clang	4m 8s
PrepareVSPlugin	2m 17s
x86_64 test-nortti	3m 41s
VerifyFormatting	23s
WindowsBuild	32m 2s
x86_64 test-c++20	3m 45s
x86_64 test-c++23	3m 18s
x86_64 smoke-test	10m 31s
arm64 smoke-test	12m 18s
x86_64 asan	5m 6s
x86_64 asan-clang	4m 37s
x86_64 compile	3m 23s
arm64 compile	3m 56s
x86_64 compile-clang	3m 12s
arm64 compile-clang	3m 52s
x86_64 compile-static	3m 17s
arm64 compile-static	3m 54s
x86_64 compile-static-clang	3m 16s
arm64 compile-static-clang	3m 47s
x86_64 clean	7m 18s
arm64 clean	7m 9s
Build and deploy GitHub pages	8s
📦 Release	0s
	3h 54m 46s

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