reducing libraries size

[6r0m]

1. there are some libraries that are not using in the build.cs (grpc++_alts, grpc++_reflection etc.)
2. also some linked by the build.cs could be deleted (from abseil group) without further build problems
3. re2 library could be pickup from EngineThirdParty
4. if make build from Linux, sizes of libraries significantly reduces:
   grpc - 150 -> 64
   protobuf - 70 -> 24
   abseil - 14 -> 5

[thejinchao]

great idea, thanks