[CI] Switch to Ubuntu 26.04 #5036

Job	Run time
ci-scope	8s
pre-commit / pre-commit	2m 4s
pre-commit / link-check	17s
mac / clang-build (Release)	2m 21s
mac / clang-build (Debug)	2m 48s
ubuntu / clang-build (ubuntu-26.04)	2m 45s
windows / clang-build	2m 34s
windows / msvc-build (Debug)	3m 49s
windows / msvc-build (Release)	2m 0s
ubuntu / gcc-build (ubuntu-26.04, Release)	2m 47s
ubuntu / gcc-build (ubuntu-26.04, Debug)	2m 16s
windows / clang-test	1m 42s
ubuntu / clang-test (ubuntu-26.04)	2m 39s
ubuntu / clang-sanitizer-build (ubuntu-26.04)	3m 2s
ubuntu / gcc-test (ubuntu-26.04)	2m 39s
mac / clang-test	1m 20s
windows / msvc-test	2m 24s
mac / clang-test-extended	1m 36s
windows / clang-test-extended	1m 42s
ubuntu / gcc-test-extended (ubuntu-26.04)	1m 54s
ubuntu / clang-test-extended (ubuntu-26.04)	1m 40s
ubuntu / clang-sanitizer-test (ubuntu-26.04)	1m 17s
windows / msvc-test-extended	1m 18s
ubuntu / clang-sanitizer-test-extended (ubuntu-26.04)	1m 13s
ubuntu / gcc-build-codecov	4m 0s
perf / ubuntu-gcc-build-perf-stats	1m 8s
perf / macos-clang-build-perf-stats	2m 7s
pages / build-doxygen-xml	13s
pages / build-scoreboard	21s
pages / build-sphinx	39s
pages / deploy-pages	0s
	56m 43s

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