fix: Solve multiple issues relating to arena mutation in SQL subqueries

[alexander-beedie]

Closes #17381.
Closes #17056.
Closes #20732.

Turns out we had an issue with possible arena/context mutation when subqueries execute.

Fixed by introducing an execute_isolated function taking a query-executing closure that ensures the subquery gets clean state, and any state updates inside the subquery don't propagate into the original/outer context.

Takes care of several outstanding issues 👍

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.75%. Comparing base (6bf4153) to head (4179db5).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25110      +/-   ##
==========================================
+ Coverage   81.03%   81.75%   +0.72%     
==========================================
  Files        1707     1707              
  Lines      235607   235630      +23     
  Branches     3005     3005              
==========================================
+ Hits       190913   192647    +1734     
+ Misses      43926    42215    -1711     
  Partials      768      768              

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