Create framework-connectivity shared filegroup

Since data usage related code is going to move to mainline module,
hidden classes and methods can no longer be accessed. However,
some of the hidden classes in the platform are still needed, and
cannot be moved because of other callers.

Thus, create a shared srcs filegroup to allow these classes
build with the module to solve the dependencies.

Test: TH
Bug: 204830222
Change-Id: I3813bc2177b2f0b4237056f64c57c63fa29c3081