Handle request retrying better

[Veykril]

Currently a bunch of request handles may panic if we retry them after document changes have come in. This is obviously quite annoying for users, we should fix this. There are two ways I can see to go forward here

1. Attach the current mem doc version of a file to requests that have files in them and bail if the versions dont line up when processing the request
2. Replay any document changes that have happened since accepting the and processing the request and attempt to adjusting the offsets in the request before processing it.
3. Replay any document changes that have happened since accepting the and processing the request and bail out if the offsets in the request may be affected.

All of these options are pretty bad, but we need to do something here unfortunately.