Port training model code into user tools

[parthosa]

Fixes #909.

We want to import the training module from QualX and update the prediction code with latest changes. This will be done in four steps.

Steps

1. Import the source code and pretrained models as it as. Exclude these from pytest and flake8 linters.
2. Make changes in the qualx files to connect them with tools.
3. Make changes in the tools to use the latest changes in qualx.
4. Add entry point for train by adding a new CMD for training.

Note:

• This PR adds the changes for Step 2.
• Base branch spark-rapids-tools-1049-base has original code imported as it is (Step 1). Commit - https://github.com/NVIDIA/spark-rapids-tools/commit/757775ec9478bc24626ea219f63b60f14bb0bc69
• Head branch spark-rapids-tools-1049-plug-qualx makes relevant changes in qualx so that we can plug it with tools.

Directory structure for QualX:

• Source code path:
  • spark-rapids-tools/user_tools/src/spark_rapids_tools/tools/qualx
• Pretrained models path:
  • spark-rapids-tools/user_tools/src/spark_rapids_pytools/resources/qualx/models/xgboost

Test:

• This PR has no impact in tools usage as we do not have function calls to any of the methods in this PR.
• Subsequent PRs would add the relevant entry points.

[leewyang]

LGTM