Add --all-shells flag to ensure_path

[gh271]

• I have added a news fragment under changelog.d/ (if the patch affects the end users)

Summary of changes

Add --all-shells flag to pipx ensure_path, see issue: #1585

Test plan

Tested by running:

$ pipx ensurepath --all-shells

I have one failing test (test_run_with_requirements):

ERROR    pipx.util:util.py:347 Fatal error from pip prevented installation. Full pip output in file:

The pip output file contains:

PIP STDOUT
----------
Looking in indexes: http://127.0.0.1:62640/simple/

PIP STDERR
----------
ERROR: Could not find a version that satisfies the requirement requests==2.31.0 (from versions: 2.32.3)
ERROR: No matching distribution found for requests==2.31.0

Unfortunately I don't know what is causing this and how I can fix it, any ideas?