speechInteraction: cleanup of cmake

[Nicogene]

This is for making it cross platform

Moreover added some dependencies via FetchContent, google speech api has still to be fixed

[vtikha]

LGTM (so far)!

[Nicogene]

I redimensioned the PR, the google API needs grpc installed in the system if using the makefile specified in the repo, or its clone and install its own if using Bazel(see https://github.com/googleapis/googleapis#building). The FetchContent has not so much sense in this case.
I left the part about googleapis untouched, since to me seems not super cmake-friendly(in fact they support and use Bazel) and I didn't find a better way to include it
In any case, now the libraries are linked as cmake targets and it is a step in the direction of making it cross-platform.