Add package data and data files to setup.py for requirements management

[sarthakpati]

This fixes #959

Summary:

Added package_data and data_files to setup.py to ensure the sdist gets created correctly.

Test plan:

Checked using a basic build command:

(base) PS C:\Projects> git clone https://github.com/sarthakpati/tnt.git tnt_mine
[SNIP!]
(base) PS C:\Projects> cd tnt_mine
(base) PS C:\Projects\tnt_mine> conda create -p ./venv python=3.11
[SNIP!]
(base) PS C:\Projects\tnt_mine> conda activate ./venv
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine> pip install build
[SNIP!]
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine> git rev-parse HEAD
5e01a89e2c41f1b63e4030bc1370d33e76b37182
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine> python -m build
[SNIP!]
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine> cd .\dist\
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine\dist> tar -xf .\torchtnt-0.2.4.tar.gz
(C:\Projects\venv\tnt_mine) PS C:\Projects\tnt_mine\dist> ls .\torchtnt-0.2.4\

    Directory: C:\Projects\tnt_mine\dist\torchtnt-0.2.4

Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d----          2025-01-15    15:20                torchtnt
d----          2025-01-15    15:20                torchtnt.egg-info
-a---          2025-01-15    15:15             70 dev-requirements.txt
-a---          2025-01-15    15:15           1563 LICENSE
-a---          2025-01-15    15:20           3381 PKG-INFO
-a---          2025-01-15    15:15             47 pyproject.toml
-a---          2025-01-15    15:15           1820 README.md
-a---          2025-01-15    15:15            133 requirements.txt
-a---          2025-01-15    15:20             42 setup.cfg
-a---          2025-01-15    15:20           3187 setup.py

Fixes #959

[sethc555]

Independent verification: with this PR checked out, python -m build (sdist → wheel) succeeds in a clean python:3.12 container with current setuptools. Without it, the published torchtnt 0.2.4 sdist is incomplete — setup.py reads requirements.txt, which is not shipped — so pip install --no-binary :all: torchtnt fails, confirming #959. Found while build-checking the top-5000 PyPI packages for source-install breakage.