pgsql: Fix ILIST_DEBUG build

Fix ILIST_DEBUG build

In c8ad4d8166a dlist_member_check()'s arguments were made const. Unfortunately
the implementation of dlist_member_check() used dlist_foreach(), which
currently doesn't work for const lists.

As a workaround, open-code the list iteration. The other check functions
already do so.

Discussion: /messages/by-id/20230118182214.co7dp4oahiunwg57@awork3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/2b16208753770318085b1201a6d101cab2697132

Modified Files
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src/backend/lib/ilist.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)