Initial ADLS gen2 support

[pjbull]

Add initial ADLS gen2 support:

• Accept or create a data_lake_service_client
• When necessary in AzureBlobClient use the data_lake_service_client API. This does not use the ADLS API everywhere possible since ADLS Gen2 works with the normal blob API in many places. Do this since it is common to enable hierarchical namespaces when creating a blob storage account, not realizing that it needs ADLS APIs for some scenarios.
• Add the ADLS SDK as a dependency
• Adds a new Azure test rig for Gen2 if configured
• Configures ADLS Gen2 testing on Github Actions

This also incorporates the fixes in:

• PR perf(az): optimize non-recursive _list_dir #447
• PR fix(az): correctly remove nested file structures #449

Closes #161

---

• Test the different instantiation pipelines
• Test empty folders on ADLS Gen2
• Fix mocks to do offline tests for ADLS Gen2 and not
• Add additionally functionality mentioned in Support Azure Data Lake Storage Gen2 #161

[github-actions]

🚀 Deployed on https://deploy-preview-453--gallant-agnesi-5f7bb3.netlify.app

[codecov]

Codecov Report

Attention: Patch coverage is 97.70115% with 2 lines in your changes missing coverage. Please review.

Project coverage is 94.2%. Comparing base (f3605a6) to head (9853b6b).
Report is 1 commits behind head on master.

Files	Patch %	Lines
cloudpathlib/azure/azblobclient.py	97.4%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff            @@
##           master    #453     +/-   ##
========================================
+ Coverage    93.6%   94.2%   +0.6%     
========================================
  Files          23      23             
  Lines        1665    1728     +63     
========================================
+ Hits         1559    1629     +70     
+ Misses        106      99      -7     

Files	Coverage Δ
cloudpathlib/azure/azblobpath.py	93.6% <100.0%> (+0.9%)	⬆️
cloudpathlib/cloudpath.py	94.5% <100.0%> (+0.3%)	⬆️
cloudpathlib/azure/azblobclient.py	96.8% <97.4%> (+2.0%)	⬆️

... and 2 files with indirect coverage changes

[pjbull]

A couple of typos/tweaks

[pjbull]

@M0dEx Thanks for your patience—ended up being more here than I expected. I think this is basically ready except a few small typos/tweaks. If you've got time, it would be great if you took this branch for a test drive and took a look at the code changes.

[pjbull]

Planning to rebase on top of #461 when that is in so that tests are reliable.

[pjbull]

@jayqi Should be ready for the release. Scope/maintenance burden is a little larger, but I think this is a large standing issue with a fair amount of interest so it is worth it to get in.

[jayqi]

Okay, it feels a little messy but I think it's reasonable.

[pjbull]

Okay, it feels a little messy but I think it's reasonable.

Truer words were never spoken.