pgsql: Improve ICU option handling in CREATE DATABASE

Improve ICU option handling in CREATE DATABASE

We check that the ICU locale is only specified if the ICU locale
provider is selected.  But we did that too early.  We need to wait
until we load the settings of the template database, since that could
also set what the locale provider is.

Reported-by: Marina Polyakova <m.polyakova@postgrespro.ru>
Discussion: https://www.postgresql.org/message-id/9ba4cd1ea6ed6b7b15c0ff15e6f540cd@postgrespro.ru

Branch
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REL_15_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/865b52af61049719e0a289419a0eceded6ea7bae

Modified Files
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src/backend/commands/dbcommands.c | 11 +++++++----
src/bin/scripts/t/020_createdb.pl |  4 ++++
2 files changed, 11 insertions(+), 4 deletions(-)