The RBTools codebase is old, and we have a lot of code that doesn't

quite follow best practices. These include functions that take a whole

lot of keyword arguments, but with calls passing values as positional

arguments instead.
Python 3 allows us to define keyword-only arguments, which can help us

clean things up, but as we aim to provide backwards-compatibility during

deprecation phases, we can't just simply use them.
This change introduces a decorator to help with this.
rbtools.deprecation.deprecate_non_keyword_only_args() can be used for

any function taking keyword-only arguments. Any call that supplies such

an argument via a positional argument value will trigger a deprecation

warning. The arguments will then be rewritten to pass those in as

keyword arguments.
We'll want this pattern for other codebases in time. Unfortunately, no

other packages we depend on provide a decorator like this, so we'll need

to maintain it ourselves. (Packages like debtcollector do not provide

anything for this.). For now, it will remain in RBTools.

Decorated some functions and tested calls with and without using

keyword arguments for the values. Verified the warnings only appeared

when passing values as positional arguments.
Verified that the warning's stack trace had the right stack level,

showing the call to the function.
Unit tests pass on Python 3.7-3.11.