pgsql: Add overflow checks to money type.

Add overflow checks to money type.

None of the arithmetic functions for the the money type handle
overflow.  This commit introduces several helper functions with
overflow checking and makes use of them in the money type's
arithmetic functions.

Fixes bug #18240.

Reported-by: Alexander Lakhin
Author: Joseph Koshakow
Discussion: https://postgr.es/m/18240-c5da758d7dc1ecf0%40postgresql.org
Discussion: https://postgr.es/m/CAAvxfHdBPOyEGS7s%2Bxf4iaW0-cgiq25jpYdWBqQqvLtLe_t6tw%40mail.gmail.com
Backpatch-through: 12

Branch
------
REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/4f962815871f6ac4eb3b516832b5c95a2f628f1b

Modified Files
--------------
src/backend/utils/adt/cash.c        | 174 +++++++++++++++++++-----------------
src/test/regress/expected/money.out |  19 ++++
src/test/regress/sql/money.sql      |  11 +++
3 files changed, 124 insertions(+), 80 deletions(-)