gst/: Change API of gst_plugin_register_static() to not take a GstPluginDesc, but rather just take all the arguments ...

Original commit message from CVS:
* gst/gst.c: (init_post):
* gst/gstplugin.c: (_gst_plugin_register_static),
(gst_plugin_register_static), (_gst_plugin_initialize):
* gst/gstplugin.h: (GstPluginFilter):
Change API of gst_plugin_register_static() to not take
a GstPluginDesc, but rather just take all the arguments
in a GstPluginDesc directly. This is more intuitive and
avoids certain mistakes when porting code from
GST_PLUGIN_DEFINE_STATIC to gst_plugin_register_static().
Fixes #510187.
* tests/check/gst/gstplugin.c:
Fix up for changed API.