feat: introduce global thread pool and rename `ShellOtps` to `GlobalOpts` #16741

Job	Run time
codespell	10s
doctest	2m 54s
crate-checks	3m 26s
docs	1m 18s
clippy	1m 19s
forge-fmt	1m 22s
rustfmt	15s
nextest / build matrices	7s
nextest / test unit (x86_64-unknown-linux-gnu)	3m 19s
nextest / test integration (1/3) (x86_64-unknown-linux-gnu)	7m 10s
nextest / test integration (2/3) (x86_64-unknown-linux-gnu)	7m 17s
nextest / test integration (3/3) (x86_64-unknown-linux-gnu)	7m 14s
nextest / test integration / issue-repros (1/2) (x86_64-unknown-linux-gnu)	5m 55s
nextest / test integration / issue-repros (2/2) (x86_64-unknown-linux-gnu)	6m 52s
nextest / test integration / external (1/2) (x86_64-unknown-linux-gnu)	6m 43s
nextest / test integration / external (2/2) (x86_64-unknown-linux-gnu)	6m 24s
nextest / test unit (x86_64-pc-windows-msvc)	7m 22s
nextest / test integration (1/3) (x86_64-pc-windows-msvc)	7m 52s
nextest / test integration (2/3) (x86_64-pc-windows-msvc)	7m 55s
nextest / test integration (3/3) (x86_64-pc-windows-msvc)	7m 55s
ci-success	8s
	1h 32m 57s

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