Automatically generating and using test INI files is supported for
in-tree build (`buildconf`) for a long time, and this can make sense
for phpize builds too, especially when the build extension is a zend
extension, so it can be properly loaded.
Thus we make `--enable-test-ini` and `--with-test-ini-ext-exclude`
available for phpize, but default to false for full BC.
Closes GH-8787.
c643cbf388