check

feat(builtin): add `Iter2::concat()` #5212

Job	Run time
build (ubuntu-latest)	3m 24s
build (macos-latest)	1m 38s
build (macos-13)	3m 49s
license-header-check	7s
coverage-check	20s
build (windows-latest)	1m 50s
bleeding-check (macos-latest)	9s
bleeding-check (ubuntu-latest)	9s
moon-json-format-check	5s
nightly-check (ubuntu-latest)	2m 33s
typo-check	3s
bleeding-check (windows-latest)	22s
nightly-check (macos-latest)	1m 41s
bleeding-check (macos-13)	12s
nightly-check (macos-13)	2m 58s
nightly-check (windows-latest)	1m 51s
	21m 11s

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