[WIP] Proper index handling for chunked reading multiple parquet files

[galipremsagar]

Fixes: #8536, #6872
This pr is WIP

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@@               Coverage Diff               @@
##             branch-21.08    #8726   +/-   ##
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  Coverage                ?   10.66%           
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  Files                   ?      109           
  Lines                   ?    18692           
  Branches                ?        0           
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  Hits                    ?     1993           
  Misses                  ?    16699           
  Partials                ?        0           

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[galipremsagar]

Moving this to 21.10 as this is a major change at the python layer that I'm not comfortable merging at the last moment.

cc: @vuule @devavret @quasiben @JohnZed

[github-actions]

This PR has been labeled inactive-90d due to no recent activity in the past 90 days. Please close this PR if it is no longer required. Otherwise, please respond with a comment indicating any updates.

[galipremsagar]

duplicate of #11105