Allow skipping pip install step in check-python

[jtpio]

Current the check-python step also tries to install the packages in a new environment with pip:

jupyter_releaser/jupyter_releaser/python.py

Lines 71 to 75 in 5c89302

	# Create the virtual env, upgrade pip,
	# install, and run test command
	util.run(f"python -m venv {env_path}")
	util.run(f"{bin_path}/python -m pip install -q -U pip")
	util.run(f"{bin_path}/pip install -q {dist_file}")

This can cause issues in Python monorepos with packages depending on each other with lower bounds, for example:

• package foo, version 0.1.2, has no dependency
• package bar, version 0.1.2 has a dependency on foo >= 0.1.2

When trying to install bar in the check-python, package foo==0.1.2 has not yet been released and bar cannot be installed.

This might also be related to #371 and #372, although not sure if they still applied after the switch to releaser v2.

[jtpio]

An alternative could also be to allow for passing extra args (for example --no-deps).