Fix installation issues

[shubhamugare]

Description of changes:

Currently, the installation of the mxeval package requires using the cloned repository. This is not ideal for other tools that will use mxeval. This PR simplifies the installation such that one can simply use pip install git+https://github.com/amazon-science/mxeval.git for installation.

The PR includes following changes:

1. Changes in setup.py to enable above.
2. Move the data directory inside the mxeval module. Updated paths in the code where data is accessed accordingly. This is necessary since the installed module will now contain the data directory.

Test:
I'm working on a tool that uses this dependency. I have tested that I could import mxeval humaneval and mbpp.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[ens-lg4]

I support this merge request.

Was about to make a similar one, then found out someone was thinking the same, but half a year earlier!

[shubhamugare]

I think they are not actively looking at the repository anymore. You can just use my fork as I did here. :)

[ens-lg4]

You can just use my fork as I did here. :)

Thanks!
This almost exactly what I just did (only with axs integration) :

axs byquery python_package,package_name=mxeval,installable=git+https://github.com/shubhamugare/mxeval.git