ext/intl: Pre-size arrays created from ICU enumerations

[kn1g78]

Use uenum_count() to pre-size arrays built from ICU enumerations.

This avoids unnecessary HashTable growth in transliterator_list_ids(),
resourcebundle_locales() and locale_get_keywords().

locale_get_keywords() also uses the keyword length reported by ICU when
inserting the associative entry, with a fallback to strlen() for unknown
lengths.

If counting fails, the previous behavior is preserved by falling back to an
unsized array initialization.

[devnexen]

I do not think you need this ternary expression count is 0 otherwise.

[devnexen]

lgtm minus the nit ; here since these are enumerations, uenum_count should not be slow but it s not a huge win neither.

[LamentXU123]

a. The min size of hashtable in Zend is 8. So array_init won't grow if the size is smaller than 8. That makes your optimization in locale_get_keyword not that much useful (it could even be slower)
b. please run a benchmark if you think this optimize codes. It is not so obvious because uenum_count can be slow either (as David mentioned). See: https://raw.githubusercontent.com/unicode-org/icu/main/icu4c/source/common/unicode/uenum.h
c. I don't love the additional complexity. (But it is good if this do speed-up things :) )

[LamentXU123]

LGTM 👍The remaining one should be obvious optimization.
Seems like the Resourceboundle one is deleted? Feel free to add it back if you have your bench results.

[kn1g78]

Use uenum_count() to pre-size arrays built from ICU enumerations in
transliterator_list_ids() and resourcebundle_locales().

falls back to an unsized array and keeps the existing iteration behavior.

locale_get_keywords() is left unchanged because those arrays are usually
small.

Local ICU-level benchmark numbers, using PHP 8.5.6RC3 + ICU 77 through FFI:

Counts: transliterator=758, resource(NULL)=881, keyword=3

utrans_openIDs + uenum_count             1.033 us/op
utrans_openIDs + full iterate         2017.807 us/op

ures_available(NULL) + uenum_count       2.916 us/op
ures_available(NULL) + full iterate    879.196 us/op

uloc_openKeywords + uenum_count          5.498 us/op
uloc_openKeywords + full iterate         8.059 us/op

[LamentXU123]

Thank you!