Fix usage of annotations in TetheringLib

Annotations such as @SystemApi cannot be jarjared to a different
package, as the members would not match the system API declarations.

Instead, only build against the annotations from
framework-annotations-lib, but do not include them as classes in the
output jar; annotations are not required to be available to the
classloader at runtime.

Test: builds, boots, tethering working
Bug: 147812912
Fixes: 148609988
Change-Id: I1fae97a1c1e0ba07fa3e2d64cde7650cd26d0acd