[gRPC] Check whether CompileReq#programmer is required

[kittaakos]

I have noticed, the CompileReq has the programmer field:

arduino-cli/rpc/commands/compile.proto

Line 43 in 3d74a8f

string programmer = 19; // External programmer for upload

One can trigger an automatic upload with the compile command from the command line by appending the -u (--upload) flag, but it is not possible to trigger an upload with the CompileReq via gRPC.

Long story short: the programmer seems superfluous. Please check whether it is needed or not.

Thank you!