GraphQL: Allow specifying Google Cloud project

app/assets/javascripts/graphql_shared/possible_types.json

doc/api/graphql/reference/index.md

ee/app/graphql/ee/types/project_type.rb

...l/resolvers/ci/runner_cloud_provisioning_base_resolver.rb

...rs/ci/runner_cloud_provisioning_machine_types_resolver.rb

...esolvers/ci/runner_cloud_provisioning_regions_resolver.rb

.../resolvers/ci/runner_cloud_provisioning_zones_resolver.rb

...raphql/types/ci/runner_cloud_provisioning_options_type.rb

...types/ci/runner_google_cloud_provisioning_options_type.rb

...pp/services/google_cloud_platform/compute/base_service.rb

...l/types/ci/runner_cloud_provisioning_options_type_spec.rb

ee/spec/graphql/types/project_type_spec.rb

ee/spec/lib/google_cloud_platform/compute/client_spec.rb

.../project/runner_google_cloud_provisioning_options_spec.rb

...cloud_platform/compute/list_machine_types_service_spec.rb

...oogle_cloud_platform/compute/list_regions_service_spec.rb

.../google_cloud_platform/compute/list_zones_service_spec.rb

...google_cloud_platform/compute/services_shared_contexts.rb

...google_cloud_platform/compute/services_shared_examples.rb