pgsql: Wrap ICU ucol_open().

Wrap ICU ucol_open().

Hide details of supporting older ICU versions in a wrapper
function. The current code only needs to handle
icu_set_collation_attributes(), but a subsequent commit will add
additional version-specific code.

Discussion: https://postgr.es/m/7ee414ad-deb5-1144-8a0e-b34ae3b71cd5@enterprisedb.com
Reviewed-by: Peter Eisentraut

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a326aac8f1719c37529ae090f66bac9e62c32346

Modified Files
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src/backend/utils/adt/pg_locale.c | 70 ++++++++++++++++++++++++---------------
1 file changed, 43 insertions(+), 27 deletions(-)