pgsql: Avoid some other O(N^2) hazards in list manipulation.

Avoid some other O(N^2) hazards in list manipulation.

In the same spirit as 6301c3ada, fix some more places where we were
using list_delete_first() in a loop and thereby risking O(N^2)
behavior. It's not clear that the lists manipulated in these spots
can get long enough to be really problematic ... but it's not clear
that they can't, either, and the fixes are simple enough.

As before, back-patch to v13.

Discussion: https://postgr.es/m/[email protected]

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/e477642a1ba8041c94cae2f8bbdb689f05cb0260

Modified Files
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contrib/pg_trgm/trgm_regexp.c | 25 +++++++++++++++++--------
src/backend/executor/nodeAgg.c | 17 +++++------------
src/backend/jit/llvm/llvmjit.c | 10 +++++-----
3 files changed, 27 insertions(+), 25 deletions(-)