Add support for detecting `$VIRTUAL_ENV` #980

Job	Run time
Tests in Containers (ci-jupyter-container, ubuntu-latest, mcr.microsoft.com/devcontainers/univers...	4m 9s
Builds (windows-latest, x86_64-pc-windows-msvc)	5m 15s
Tests in Containers (ci-homebrew-container, ubuntu-latest, homebrew/brew, x86_64-unknown-linux-musl)	3m 28s
Builds (windows-latest, aarch64-pc-windows-msvc)	3m 48s
Builds (ubuntu-latest, x86_64-unknown-linux-musl, yes)	2m 0s
Env Tests (ci-poetry-global, ubuntu-latest, x86_64-unknown-linux-musl)	2m 22s
Builds (macos-latest, x86_64-apple-darwin, yes)	2m 6s
Env Tests (ci-poetry-project, ubuntu-latest, x86_64-unknown-linux-musl)	2m 22s
Builds (macos-14, aarch64-apple-darwin, yes)	2m 1s
Env Tests (ci-poetry-custom, ubuntu-latest, x86_64-unknown-linux-musl)	2m 18s
Env Tests (ci-poetry-global, windows-latest, x86_64-pc-windows-msvc)	6m 57s
Tests (windows-latest, x86_64-pc-windows-msvc, yes)	9m 58s
Env Tests (ci-poetry-project, windows-latest, x86_64-pc-windows-msvc)	7m 20s
Tests (ubuntu-latest, x86_64-unknown-linux-musl, yes)	9m 46s
Env Tests (ci-poetry-custom, windows-latest, x86_64-pc-windows-msvc)	6m 59s
Tests (macos-latest, x86_64-apple-darwin, yes)	11m 24s
Tests (macos-14, aarch64-apple-darwin, yes)	10m 32s
	1h 32m 45s

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