Use generic_printstr from ada_language::printstr

Use generic_printstr from ada_language::printstr

Currently, if you create a lazy string while in Ada language mode, the
string will be rendered strangely, like:

    "["d0"]["9f"]["d1"]["80"]["d0"]["b8"]...

This happens because ada_printstr does not really handle UTF-8
decoding.

This patch changes ada_language::printstr to use generic_printstr when
UTF-8 is used.

Note that this code could probably be improved some more -- the
current patch only addresses the narrow case of the Python API.  I've
filed a follow-up bug (PR ada/32413) for the remaining changes.

Approved-By: Andrew Burgess <aburgess@redhat.com>