pgsql: Remove make_temptable_name_n().

Remove make_temptable_name_n().

This small function is only used in one place, and it fails to
handle quoted table names (although the table name portion of the
input should never be quoted in current usage). In addition to
removing make_temptable_name_n() in favor of open-coding it where
needed, this commit ensures the "diff" table name is properly
quoted in order to future-proof this area a bit.

Author: Aleksander Alekseev <aleksander(at)tigerdata(dot)com>
Reviewed-by: Álvaro Herrera <alvherre(at)kurilemu(dot)de>
Reviewed-by: Shinya Kato <shinya11(dot)kato(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAJ7c6TO3a5q2NKRsjdJ6sLf8isVe4aMaaX1-Hj2TdHdhFw8zRA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4c5e1d0785ce150c3e6c65b009ea56815acbc8cd

Modified Files
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src/backend/commands/matview.c | 40 ++++++++++++++--------------------------
1 file changed, 14 insertions(+), 26 deletions(-)