Set object table index for from_dask_dataframe

[wilsonbb]

In the loader method from_dask_dataframe, we were mistakenly not updating the object table's index in the case where the object table is supplied as an argument rather than generated from the source table.

Unit tests are updated based on the identifying issue #230 validating the case where the object table isn't generated and that analysis functions can be called on the generated ensemble.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (897a5cf) 92.57% compared to head (15cdf60) 92.57%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #231   +/-   ##
=======================================
  Coverage   92.57%   92.57%           
=======================================
  Files          22       22           
  Lines        1132     1132           
=======================================
  Hits         1048     1048           
  Misses         84       84           

Files Changed	Coverage Δ
src/tape/ensemble.py	89.46% <100.00%> (ø)

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[hombit]

Looks great! The only minor issue is a warning in the case of pre-existing index

dask/dataframe/core.py:5251: UserWarning: New index has same name as existing, this is a no-op.
  warnings.warn(

[dougbrn]

Looks good!

[wilsonbb]

Looks great! The only minor issue is a warning in the case of pre-existing index

dask/dataframe/core.py:5251: UserWarning: New index has same name as existing, this is a no-op.
  warnings.warn(

Considering this some more, I've decided to open an issue to clarify documentation or provide a parameter to allow users to force the indices to be overridden: #232

However I will go ahead and submit this PR as is while I think about the interface a bit more.

Thanks for the reviews!