Allow skipping maintenance tasks for list command

[Gitznik]

• I have added an entry to docs/changelog.md

Summary of changes

Add a --skip-maintenance flag to the list command. This sets a new state on the _SharedLibs class, that is used to skip the shared libs upgrade step by setting needs_upgrade to False. This change allows the user to skip the functionality that reaches out to pip, which makes executing the command a lot faster when offline.
resolves #1081

Test plan

Introduced a new test case test_skip_maintenance. It first adds some packages to introduce shared libs. It then verifies that a normal list command sets the expected state on the shared_libs object. Then it verifies that running list with --skip-maintenance results in state on the shared_libs object that indicates that no upgrade was performed.

Tested by running nox -s tests-3.12

pipx list --skip-maintenance

[chrysle]

Concerning the test, probably really collect the times after running the CLI, and compare the durations.

[Gitznik]

Concerning the test, probably really collect the times after running the CLI, and compare the durations.

I did this manually:
python3 src/pipx list --skip-maintenance 0.42s user 0.14s system 87% cpu 0.638 total
vs with maintenance
python3 src/pipx list 0.72s user 0.21s system 10% cpu 8.623 total
when running offline and being in a state that would require an upgrade.

Do you have a suggestion on how to automate this with a test? My only suggestion would be to modify pipx_temp_env to allow creating an unresponsive local pypi server, but that feels like a lot of custom logic for one test.

[gaborbernat]

[gaborbernat]

Needs merge conflicts fixed and rebased.

[Gitznik]

Needs merge conflicts fixed and rebased.

Done