[cont'd] Configure services with envs

[ilgooz]

this pr will be split to small ones as:

• simplify interface/grpc/core>deploy implementation & use options in protobuf/coreapi>DeployService
• api>deploy: pass env variables as an Option
• service: pass env variables as an Option
• service: return all validation errors for deploy time env vars & add tests
• x/osx: rm unneeded cap
• commands>deploy: add unit tests including env vars

[NicolasMahe]

@ilgooz could you split this PR into multiple small one please?
I agree with most of the change but not all so it will be easier split this PR into small ones.

[ilgooz]

this PR split into smaller ones as described in the first message