refactor: update PyVenvCfg to use Option types for version fields and adjust related logic #1279

Job	Run time
Tests in Containers (ci-jupyter-container, ubuntu-latest, mcr.microsoft.com/devcontainers/univers...	4m 30s
Tests in Containers (ci-homebrew-container, ubuntu-latest, homebrew/brew, x86_64-unknown-linux-musl)	3m 42s
Tests (ubuntu-latest, x86_64-unknown-linux-musl, yes)	8m 35s
Builds (windows-latest, x86_64-pc-windows-msvc)	4m 36s
Tests (macos-latest, x86_64-apple-darwin, yes)	12m 20s
Tests (macos-14, aarch64-apple-darwin, yes)	13m 37s
Builds (ubuntu-latest, x86_64-unknown-linux-musl, yes)	2m 7s
Tests (windows-latest, x86_64-pc-windows-msvc, yes)	10m 29s
Builds (macos-14, aarch64-apple-darwin, yes)	3m 21s
Builds (windows-latest, aarch64-pc-windows-msvc)	4m 42s
Builds (macos-latest, x86_64-apple-darwin, yes)	3m 20s
Env Tests (ci-poetry-project, windows-latest, x86_64-pc-windows-msvc)	5m 36s
Env Tests (ci-poetry-custom, windows-latest, x86_64-pc-windows-msvc)	5m 40s
Env Tests (ci-poetry-project, ubuntu-latest, x86_64-unknown-linux-musl)	2m 47s
Env Tests (ci-poetry-global, windows-latest, x86_64-pc-windows-msvc)	5m 43s
Env Tests (ci-poetry-global, ubuntu-latest, x86_64-unknown-linux-musl)	2m 39s
Env Tests (ci-poetry-custom, ubuntu-latest, x86_64-unknown-linux-musl)	2m 53s
	1h 36m 37s

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