Bundle newer libpq dll in Windows installer

[jng]

Currently when building the Windows installer, we re-purpose the libpq.dll provided by the bundled PHP for use with the PostgreSQL FDO provider if enabled.

However, this version of libpq.dll is not the latest and doesn't connect to the latest PostgreSQL 16 servers and will leave an unpleasant experience for users who were expecting the PostgreSQL FDO provider to be working "out of the box" with the latest version of PostgreSQL.

To avoid this unexpected behaviour and to eliminate the need for end-users to have to dll swap libpq.dll with a newer version, let's just do the work for them and just bundle the latest libpq.dll into the Windows installer.

[jng]

Fixed r10095