Have a iree_runtime_size_benchmark target and track its size

We should be able to have a minimal target that pulls in the dylib backend, no flags, no logging, etc and just uses iree_vm_invoke to call a model, similar to the existing iree/vm/bytecode_module_size_benchmark. The intent is to see what the impact of a standalone IREE build is to a user's application size. Even better would be another standard_library_size_benchmark that was just main() and pulled in a few things that we can reasonably expect any integrator to already have (like printf, std::string/std::vector as used by our current C++ code, etc). Diffing those two will give us the delta IREE adds to an average application.

@hanhanW I feel like you were playing with some benchmark tracking stuff at some point - could we potentially feed the byte size values to the same thing as time values and get size-over-time tracking?

We should be compiling with Release or MinSizeRel in cmake as that is what anyone integrating us will be using.