Adapt to gdbrunner packaging.

Similar to
https://android-review.googlesource.com/c/platform/build/+/2403120.
The directory structure of //development/python-packages/gdbrunner
needs to change to be able to export type info to importers, and this
needs to adapt to keep gdbclient working.

Bug: None
Test: gdbclient.py --help
Change-Id: I8127ec7beae2a7840283be25ee236a8e2af48cae