docs: simplify data downloading and add mlflow to uplift modelling

[thinkall]

Related Issues/PRs

None

What changes are proposed in this pull request?

• Simplified data downloading section in notebooks.
• Added mlflow logging and loading to uplift modelling sample.
• Updated saving dataframe with delta format.

How is this patch tested?

• [x] I have written tests (not required for typo or doc fix) and confirmed the proposed feature/bug-fix/change works.

Does this PR change any dependencies?

• [x] No. You can skip this section.
• [ ] Yes. Make sure the dependencies are resolved correctly, and list changes here.

Does this PR add a new feature? If so, have you added samples on website?

• [x] No. You can skip this section.
• [ ] Yes. Make sure you have added samples following below steps.

1. Find the corresponding markdown file for your new feature in website/docs/documentation folder. Make sure you choose the correct class estimators/transformers and namespace.
2. Follow the pattern in markdown file and add another section for your new API, including pyspark, scala (and .NET potentially) samples.
3. Make sure the DocTable points to correct API link.
4. Navigate to website folder, and run yarn run start to make sure the website renders correctly.
5. Don't forget to add <!--pytest-codeblocks:cont--> before each python code blocks to enable auto-tests for python samples.
6. Make sure the WebsiteSamplesTests job pass in the pipeline.

AB#1991714

[github-actions[bot]]

Hey @thinkall :wave:! Thank you so much for contributing to our repository :raised_hands:. Someone from SynapseML Team will be reviewing this pull request soon. We appreciate your patience and contributions :100:!

[thinkall]

/azp run

[azure-pipelines[bot]]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov-commenter]

Codecov Report

Merging #1659 (86ccb72) into master (95f451a) will increase coverage by 0.03%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1659      +/-   ##
==========================================
+ Coverage   85.60%   85.63%   +0.03%     
==========================================
  Files         272      272              
  Lines       14230    14230              
  Branches      739      739              
==========================================
+ Hits        12181    12186       +5     
+ Misses       2049     2044       -5     

Impacted Files	Coverage Δ
...zure/synapse/ml/stages/PartitionConsolidator.scala	95.74% <0.00%> (-2.13%)	:arrow_down:
.../azure/synapse/ml/downloader/ModelDownloader.scala	88.88% <0.00%> (+1.23%)	:arrow_up:
...crosoft/azure/synapse/ml/io/http/HTTPClients.scala	75.00% <0.00%> (+7.35%)	:arrow_up:

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