Allow apply udf to reference global modules in cudf.pandas

[mroeschke]

Description

closes #15548

_replace_closurevars creates a new function by replacing objects with their fast versions. When creating the new function, it populates globals from the result of inspect.getclosurevars, but it don't think it comprehensively returns all the globals accessible to the function (function.__globals__)

To minimize the change, the "fast globals" are still sourced from inspect.getclosurevars, and those update the old_function.__globals__ when creating a new function.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[mroeschke]

/merge