[GIT-PULLS] [php-src] PR #23318: Fix GH-23094: Use byte offsets in NumberFormatter parsing

Pull Request: https://github.com/php/php-src/pull/23318
Author: ColumbusLabs

Fixes #23094.

PHP exposes NumberFormatter parsing offsets as UTF-8 byte offsets, while ICU expects UTF-16 code-unit positions. Convert the input offset before parsing and the returned offset afterward for both parse() and parseCurrency().

This targets PHP-8.4 as the lowest actively supported branch; the equivalent C++ change can be merged upward.

Tests:
- debug + ZTS build with ICU 78.3
- sapi/cli/php run-tests.php ext/intl/tests/gh23094.phpt ext/intl/tests/formatter_parse.phpt ext/intl/tests/formatter_parse_currency.phpt
- sapi/cli/php run-tests.php ext/intl/tests (437 passed, 111 skipped, 1 expected failure, 0 failures)