Add `activate-environment` option #437

Job	Run time
environment-activation-explicit-env	11s
environment-activation-false	5s
environment-activation-multiple-env	14s
environment-activation-unix (ubuntu-latest)	4s
environment-activation-unix (macos-latest)	10s
environment-activation-windows-bash	16s
environment-activation-windows-cmd	13s
environment-activation-windows-pwsh	19s
	1m 32s

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