fix crash with pgaudit

[aykut-bozkurt]

There is an incompatibility between pgaudit and COPY commands. pgaudit expects its own prev_standardUtility to be called before the executor permission check hook is called. However, our COPY command does not call prev_standardUtility, so pgaudit crashes. Instead, here we disable pgaudit for the duration of the COPY command. See pgaudit/pgaudit#212

An example flow to trigger crash before this PR:

CREATE TABLE test(a int);
COPY (SELECT 1) TO '/tmp/test.parquet';
SET audit.log TO 'write';
COPY test FROM '/tmp/test.parquet';

After this PR, the crash won't happen but at the cost of not auditing "copy from parquet" commands.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.32%. Comparing base (6b5a0d5) to head (1db3e9b).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #137      +/-   ##
==========================================
+ Coverage   91.30%   91.32%   +0.02%     
==========================================
  Files          91       91              
  Lines       13153    13194      +41     
==========================================
+ Hits        12009    12050      +41     
  Misses       1144     1144              

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[onderkalaci]

maybe add a changelog entry or expand commit message that COPY commands are not audited with pgaudit anymore.