[GIT-PULLS] [php-src] PR #23445: Fix GH-23444: pdo_odbc does not convert Unicode data outside Windows

Pull Request: https://github.com/php/php-src/pull/23445
Author: lazerg

`PDO::ODBC_ATTR_ASSUME_UTF8` binds wide (`SQL_WCHAR`/`SQL_WVARCHAR`) parameters and columns as `SQL_C_BINARY` so that pdo_odbc can do the UTF-8 conversion itself. Both halves of that conversion, `pdo_odbc_utf82ucs2()` and `pdo_odbc_ucs22utf8()`, sit inside `#ifdef PHP_WIN32` and are `MultiByteToWideChar()` calls. Everywhere else they return `PDO_ODBC_CONV_NOT_REQUIRED` and nothing is converted, so raw UTF-8 reaches the server for an `nvarchar` parameter and raw UTF-16 comes back for an `nvarchar` column. With msodbcsql18 a non-ASCII parameter whose byte length is odd is rejected with `HY090`.

Both helpers are now plain UTF-8 to UTF-16 conversions with no platform code. The data-at-exec branch also needed fixing: it declared the unconverted byte length in `SQL_LEN_DATA_AT_EXEC()` while `SQLPutData()` then sent the converted bytes, which the server rejects with `22026`.

Verified against SQL Server 2025 and ODBC Driver 18 through unixODBC 2.3.14 on macOS: parameters, `LIKE` patterns and fetched column values all round-trip, including characters outside the BMP. `ext/pdo_odbc/tests` is green with that DSN, and unchanged against the SQLite3 ODBC driver.

One thing worth separating out from the report: the `N'…'` literal inside the query text in that snippet is mangled before it reaches the server, because unixODBC transcodes the statement text using the process locale's charset and PHP runs in the C locale. That is a different problem from the bound parameter and is not addressed here.

Fixes GH-23444