[libui] Create a libui-types static library.

This is intended to be a small library for sharing some libui types with
APEX modules. I.e., HIDL dependencies such as gralloc should not be
included in the library so that binary sizes remain small.

Bug: 136263238
Test: builds
Change-Id: I9d9d5fb32033c08cfb517f6cfc0ecb4cf1eee2fe