Generalize table check in _get_tables_from_stack

[charlesbluca]

Allows us to remove xfail from the GPU case in test_tables_from_stack

[codecov-commenter]

Codecov Report

Merging #333 (79cf0cf) into main (0c05787) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #333   +/-   ##
=======================================
  Coverage   95.74%   95.74%           
=======================================
  Files          65       65           
  Lines        2841     2841           
  Branches      429      429           
=======================================
  Hits         2720     2720           
  Misses         75       75           
  Partials       46       46           

Impacted Files	Coverage Δ
dask_sql/context.py	99.13% <100.00%> (ø)

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