Adopt ~Copyable in `Subprocess` #21

Job	Run time
Test / macOS (Xcode 16.3 - sequoia - ARM64)	42s
Test / Windows (6.1 - windows-2022)	12m 59s
Test / Linux (6.1 - noble)	50s
Test / Windows (nightly-main - windows-2019)	11m 15s
Test / Linux (6.1 - jammy)	58s
Test / Linux (6.1 - focal)	1m 9s
Test / Linux (6.1 - rhel-ubi9)	1m 14s
Test / Linux (nightly-main - noble)	1m 4s
Test / Linux (nightly-main - jammy)	1m 18s
Test / Linux (nightly-main - focal)	1m 1s
Test / Linux (nightly-main - rhel-ubi9)	2m 9s
Soundness / API breakage check	0s
Soundness / Broken symlinks check	2s
Soundness / Documentation check	0s
Soundness / Format check	0s
Soundness / License headers check	5s
Soundness / Python lint check	6s
Soundness / Shell check	48s
Soundness / Unacceptable language check	0s
Soundness / YAML lint check	4s
	35m 44s

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