feat: generates Dart language clients

[cloudwheels]

Generate dart platform & core grpc clients using the protocol buffer complier (protoc) in the image thethingsindustries/protoc

How Has This Been Tested?

Successfully generates clients which have been used to implement methods in a dart library

Breaking Changes

Checklist:

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have added or updated relevant unit/integration/functional/e2e tests
• I have made corresponding changes to the documentation

For repository code-owners and collaborators only

• I have assigned this pull request to a milestone

[shumkov]

Thank you for PR! The name of it must follow https://www.conventionalcommits.org/en/v1.0.0/

[cloudwheels]

@shumkov thanks - I have renamed commit from "feature: ..." to "feat: ..." - checks now passing!

[shumkov]

@cloudwheels You also need to commit generated code and wrap it to dart package manager packet

[shumkov]

@cloudwheels this repo is moved to https://github.com/dashevo/platform/tree/v0.22-dev/packages/dapi-grpc so please recreate your PR there.