Don't copy compressed slot to compressed batch struct

[akuzm]

There is overhead associated with copying the heap tuple and (un)pinning the respective heap buffers, which becomes apparent in vectorized aggregation.

Instead of this, it is enough to copy the by-reference segmentby values to the per-batch context.

Also we have to copy in the rare case where the compressed data is inlined into the compressed row and not toasted.

No changes in performance, as expected: https://grafana.ops.savannah-dev.timescale.com/d/fasYic_4z/compare-akuzm?orgId=1&var-branch=All&var-run1=3407&var-run2=3411&var-threshold=0&var-use_historical_thresholds=true&var-threshold_expression=2.5%20%2A%20percentile_cont%280.90%29&var-exact_suite_version=false

Disable-check: force-changelog-file

[codecov]

Codecov Report

Attention: Patch coverage is 84.78261% with 7 lines in your changes are missing coverage. Please review.

Project coverage is 80.92%. Comparing base (59f50f2) to head (ab82a22).
Report is 97 commits behind head on main.

Files	Patch %	Lines
tsl/src/nodes/decompress_chunk/compressed_batch.c	81.08%	6 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6806      +/-   ##
==========================================
+ Coverage   80.06%   80.92%   +0.85%     
==========================================
  Files         190      194       +4     
  Lines       37181    36854     -327     
  Branches     9450     9645     +195     
==========================================
+ Hits        29770    29823      +53     
- Misses       2997     3182     +185     
+ Partials     4414     3849     -565     

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[svenklemm]

probably wanna remove that

[svenklemm]

Should remove the commented out debug statements before merging