gdb: gdbarch*.py, copyright.py: add type annotations

gdb: gdbarch*.py, copyright.py: add type annotations

Add type annotations to gdbarch*.py to fix all errors shown by pyright.
There is one change in copyright.py too, to fix this one:

    /home/simark/src/binutils-gdb/gdb/gdbarch.py
      /home/simark/src/binutils-gdb/gdb/gdbarch.py:206:13 - error: Type of "copyright" is partially unknown
        Type of "copyright" is "(tool: Unknown, description: Unknown) -> str" (reportUnknownMemberType)

Change-Id: Ia109b53e267f6e2f5bd79a1288d0d5c9508c9ac4
Reviewed-By: Tom Tromey <tom@tromey.com>
Reviewed-By: Andrew Burgess <aburgess@redhat.com>