pgsql: Fix memory leak with lower,upper and initcap with ICU-provided

Fix memory leak with lower, upper and initcap with ICU-provided collations

The leak happens in str_tolower, str_toupper and str_initcap, which are
used in several places including their equivalent SQL-level functions,
and can only be triggered when using an ICU-provided collation when
converting the input string.

b615920 fixed a similar leak.  Backpatch down 10 where ICU collations
have been introduced.

Author: Konstantin Knizhnik
Discussion: https://postgr.es/m/94c0ad0a-cbc2-e4a3-7829-2bdeaf9146db@postgrespro.ru
Backpatch-through: 10

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/5380719f931a101a6e83efc7a1664e42bd6bf6c3

Modified Files
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src/backend/utils/adt/formatting.c | 3 +++
1 file changed, 3 insertions(+)