Remove namespace directives from util headers #3362

Job	Run time
lint / clang-format	15s
lint / python-lint	8s
lint / shell-lint	10s
ubuntu / clang-build (ubuntu-24.04-arm)	3m 0s
ubuntu / clang-build (ubuntu-24.04)	1m 31s
ubuntu / gcc-build (ubuntu-24.04, Debug)	2m 21s
ubuntu / gcc-build (ubuntu-24.04, Release)	1m 26s
mac / clang-build (Release)	2m 18s
windows / clang-build	2m 16s
ubuntu / gcc-build (ubuntu-24.04-arm, Release)	2m 23s
ubuntu / gcc-build (ubuntu-24.04-arm, Debug)	2m 33s
windows / msvc-build (Debug)	6m 0s
mac / clang-build (Debug)	2m 3s
windows / msvc-build (Release)	7m 27s
windows / clang-test	2m 3s
mac / clang-test	3m 17s
windows / msvc-test	3m 1s
ubuntu / clang-test (ubuntu-24.04)	5m 12s
ubuntu / clang-sanitizer-build (ubuntu-24.04)	2m 12s
ubuntu / clang-test (ubuntu-24.04-arm)	5m 45s
ubuntu / gcc-test (ubuntu-24.04-arm)	5m 52s
ubuntu / gcc-test (ubuntu-24.04)	4m 57s
mac / clang-test-extended	2m 37s
windows / clang-test-extended	2m 28s
ubuntu / clang-sanitizer-test (ubuntu-24.04)	2m 13s
windows / msvc-test-extended	2m 5s
ubuntu / clang-test-extended (ubuntu-24.04)	3m 43s
ubuntu / clang-test-extended (ubuntu-24.04-arm)	3m 39s
ubuntu / gcc-test-extended (ubuntu-24.04)	2m 54s
ubuntu / gcc-test-extended (ubuntu-24.04-arm)	3m 16s
ubuntu / clang-sanitizer-test-extended (ubuntu-24.04)	1m 49s
ubuntu / gcc-build-codecov	5m 12s
perf / ubuntu-gcc-build-perf-stats	2m 21s
pages / build-scoreboard	16s
pages / build-doxygen-xml	24s
pages / build-sphinx	1m 37s
pages / deploy-pages	0s
	1h 40m 44s

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