Hide static from cc_library_shared and vice versa

The static properties don't make sense for cc_library_shared
modules, and the shared properties don't make sense for
cc_library_static modules.  Move them into separate property
structs so they can be added conditionally.

Test: m nothing
Test: DefaultsTest
Change-Id: I0b0cedf9eba07deb721fae138ffa7bedcfbfe71e