Support glob patterns when configuring `mypy_path`

Feature

Support the glob patterns * and ** in the mypy_path configuration.

Should work the same way as it does for the files configuration.

Pitch
I have a monorepo, with a bunch of python libraries located in a directory called libs.
All packages are namespace packages with the same namespace, but they are kept in their own directory inside of the libs directory:

repository_root
│
└───libs
│   └───pkg-a
│   |    └───namespace
│   |
│   └───pkg-b
│   |    └───namespace
│   |
│   └───pkg-c
│        └───namespace
│
└───mypy.ini

The mypy_path declaration in my mypy.ini looks something like this (but with dozens of packages):

mypy_path = $MYPY_CONFIG_FILE_DIR/libs/pkg-a:
    $MYPY_CONFIG_FILE_DIR/libs/pkg-b:
    $MYPY_CONFIG_FILE_DIR/libs/pkg-c:

It would be very convenient to use a glob pattern like this instead:

mypy_path = $MYPY_CONFIG_FILE_DIR/libs/*

It's more concise, and would avoid potential problems with forgetting to include a newly added package in mypy_path.

Thanks for a great tool!

Start by tracing how glob patterns are supported for the files configuration and identify the corresponding mypy_path parsing and resolution entry points. Extend the behavior so * and ** work there too, then verify that the namespace-package monorepo example resolves all matching library directories.