Put vectorized aggregation results in short-lived memory context

[akuzm]

It is enough to use the per-tuple context for them, now they end up in the ExecutorState context which is incorrect.

Disable-check: force-changelog-file

[codecov]

Codecov Report

Attention: Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.

Project coverage is 82.12%. Comparing base (59f50f2) to head (f723cf5).
Report is 613 commits behind head on main.

Files with missing lines	Patch %	Lines
tsl/src/nodes/vector_agg/exec.c	90.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7461      +/-   ##
==========================================
+ Coverage   80.06%   82.12%   +2.05%     
==========================================
  Files         190      230      +40     
  Lines       37181    43110    +5929     
  Branches     9450    10830    +1380     
==========================================
+ Hits        29770    35404    +5634     
- Misses       2997     3396     +399     
+ Partials     4414     4310     -104     

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