Don’t return edits from `ExecuteCommandRequest`

[ahoppen]

Currently, the ExecuteCommandRequest is returning the edits it wants to perform to the source file as the LSPAny response. Clients shouldn’t know how to interpret that LSPAny and the edits are actually applied by sending a ApplyEditRequest to the client.

Only tests are currently relying on the response of the ExecuteCommandRequest. We should change those tests to test the actual ApplyEditRequest sent to the client and make ExecuteCommandRequest return an empty response.

[ahoppen]

Synced to Apple’s issue tracker as rdar://130207754