Support package and module in config file

[sameer-here]

Description

Closes#10728

Specifying module(s) to check was supported only via CLI, this PR adds
the ability to specify a module from a config file.

Test Plan

This is a pretty small change, I tested it by creating a mypy.ini file and verifying that adding the new options leads to expected outcomes (for example, specifying a package and files together will error here

mypy/mypy/main.py

Lines 957 to 960 in ea93326

	ifcode_methods==0andnotoptions.install_types:
	parser.error("Missing target module, package, files, or command.")
	elifcode_methods>1:
	parser.error("May only specify one of: module/package, files, or command.")

). If there's a unit test to which I should contribute, I'd be happy to.

Do I need to rebuild the documentation after changing config_file.rst? If so, how is that done?

Thanks!

[hauntsaninja]

Thanks, this looks reasonable. Can we make packages and modules plural everywhere for consistency with files and the option names?

[sameer-here]

@hauntsaninja looks like all checks are passing, is anything else needed?

[github-actions]

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

[hauntsaninja]

Thanks for working on this!