Respect workspace-wide requires-python in interpreter selection

[charliermarsh]

Summary

Closes #4296.

Test Plan

Ran cargo run lock --verbose from scripts/workspaces/albatross-virtual-workspace:

DEBUG uv 0.2.11 (ef3bc1612 2024-06-12)
warning: `uv lock` is experimental and may change without warning.
DEBUG Found workspace root: `/Users/crmarsh/workspace/puffin/scripts/workspaces/albatross-virtual-workspace`
DEBUG Adding discovered workspace member: /Users/crmarsh/workspace/puffin/scripts/workspaces/albatross-virtual-workspace/packages/albatross
DEBUG Adding discovered workspace member: /Users/crmarsh/workspace/puffin/scripts/workspaces/albatross-virtual-workspace/packages/bird-feeder
DEBUG Adding discovered workspace member: /Users/crmarsh/workspace/puffin/scripts/workspaces/albatross-virtual-workspace/packages/seeds
DEBUG Searching for Python >=3.12 in search path or managed toolchains
DEBUG Searching for managed toolchains at `/Users/crmarsh/Library/Application Support/uv/toolchains`
DEBUG Found managed toolchain `cpython-3.12.3-macos-aarch64-none`
DEBUG Found CPython 3.12.3 at `/Users/crmarsh/Library/Application Support/uv/toolchains/cpython-3.12.3-macos-aarch64-none/install/bin/python3` (managed toolchains)
Using Python 3.12.3 interpreter at: /Users/crmarsh/Library/Application Support/uv/toolchains/cpython-3.12.3-macos-aarch64-none/install/bin/python3

[charliermarsh]

Something that needs coverage as part of #3943.