Expose Python standard module __file__ and __name__ to rezconfig

[mottosso]

Now users can fetch the absolute path to a given rezconfig like from any other module.

rezconfig.py

import os
print("The name of this rezconfig is %s" % __name__)
print("The absolute path is: %s" % os.path.dirname(__file__))

The __name__ is computed rather than hardcoded, to account for REZ_CONFIG_FILE being able to take any arbitrary file name, along with avoiding anything hardcoded.

This is expected but missing behavior I think, but additionally one specific usecase was having my rezconfig.py at the root of my Rez packages, and wanting to set paths up relative this file.

/server/packages/rezconfig.py
/server/packages/int
/server/packages/ext

Oh, and I explicitly did not let these get carried into the resulting Config object, as that would make less sense, considering it is a result of potentially many different rezconfig.py files. Hence, writing a test for this was challenging.. if you have any ideas, I'd be happy to add some.

[mottosso]

20 days later, could we merge this? It's the tiniest of changes.