pgsql: Detect integer overflow in array_set_slice().

Detect integer overflow in array_set_slice().

When provided an empty initial array, array_set_slice() fails to
check for overflow when computing the new array's dimensions.
While such overflows are ordinarily caught by ArrayGetNItems(),
commands with the following form are accepted:

        INSERT INTO t (i[-2147483648:2147483647]) VALUES ('{}');

To fix, perform the hazardous computations using overflow-detecting
arithmetic routines.  As with commit 18b585155a, the added test
cases generate errors that include a platform-dependent value, so
we again use psql's VERBOSITY parameter to suppress printing the
message text.

Reported-by: Alexander Lakhin
Author: Joseph Koshakow
Reviewed-by: Jian He
Discussion: https://postgr.es/m/31ad2cd1-db94-bdb3-f91a-65ffdb4bef95%40gmail.com
Backpatch-through: 12

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a57d168653900903e8b1b4fe91d62de2c2f2693d

Modified Files
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src/backend/utils/adt/arrayfuncs.c   | 9 ++++++++-
src/test/regress/expected/arrays.out | 4 ++++
src/test/regress/sql/arrays.sql      | 2 ++
3 files changed, 14 insertions(+), 1 deletion(-)