Add support for sysprop description files to c++

From now on, a c++ shared library can be built only with adding
".sysprop" description file to srcs. Sysprop library generator will
automatically generate a .cpp and .h files, and the header file will be
exposed to any clients linking against the shared library. For the full
schema of description file, see system/tools/sysprop/sysprop.proto.

Bug: 80125326
Test: 1) write a .sysprop description file.
2) create cc_library_shared and add description file to srcs.
3) create another module, link against library of 2), include generated
header, and access generated sysprop functions
4) see compile succeeded.

Change-Id: I95005a0724aeb8f11a856b7aee92787a16a5374d