FindRemoteRepository is storage scoped

The contract of FindRemoteRepository RPC changed and now
it expects 'storage_name' field to be passed.
It is optional as of now, but will be made required after
migrating this RPC from SERVER scope to STORAGE scope.

Related to: https://gitlab.com/gitlab-org/gitaly/-/issues/2442

changelogs/unreleased/ps-find-remote-is-storage-scoped.yml

+---
+title: FindRemoteRepository is storage scoped
+merge_request: 35962
+author:
+type: added

lib/gitlab/gitaly_client/remote_service.rb

@@ -8,9 +8,11 @@ module Gitlab
       MAX_MSG_SIZE = 128.kilobytes.freeze
 
       def self.exists?(remote_url)
-        request = Gitaly::FindRemoteRepositoryRequest.new(remote: remote_url)
+        storage = GitalyClient.random_storage
 
-        response = GitalyClient.call(GitalyClient.random_storage,
+        request = Gitaly::FindRemoteRepositoryRequest.new(remote: remote_url, storage_name: storage)
+
+        response = GitalyClient.call(storage,
                                      :remote_service,
                                      :find_remote_repository, request,
                                      timeout: GitalyClient.medium_timeout)

spec/lib/gitlab/gitaly_client/remote_service_spec.rb

@@ -73,8 +73,11 @@ RSpec.describe Gitlab::GitalyClient::RemoteService do
   describe '.exists?' do
     context "when the remote doesn't exist" do
       let(:url) { 'https://gitlab.com/gitlab-org/ik-besta-niet-of-ik-word-geplaagd.git' }
+      let(:storage_name) { 'default' }
 
       it 'returns false' do
+        expect(Gitaly::FindRemoteRepositoryRequest).to receive(:new).with(remote: url, storage_name: storage_name).and_call_original
+
         expect(described_class.exists?(url)).to be(false)
       end
     end