Remove a bunch of incomplete widgets instead of porting them to GTK4

TalkatuMenuToolButton and TalkatuToolDrawer were mean to be used to mimic the
condensed format bar that is in Pidgin 2, but it never worked right and we'll
probably revisit the toolbar in the near future.

TalkatuMessageActions was intended to be used as an anchor widget in the
history when the history was still GtkTextView based. Now that the history is
based on GtkListBox this is no longer necessary.

Testing Done:
This was originally built against the default branch where it was compiled without any warning/errors and passed the unit tests.

Reviewed at https://reviews.imfreedom.org/r/1237/