LSP log replay

[lnicola]

In some cases like incremental text sync issues we might get desynchronized from the client state. This may or may not be the case in #10138, but having a copy of the code and a full LSP trace might help reproduce these issues.

Unfortunately, doing this isn't as easy as it seems:

• parsing the file should be easy, it's JSON per line with a prefix

• we need to remap all the file paths

• we need to make sure that the log file is line-buffered

• the ordering matters; we can extract most of it out of the log but it can still be a problem, e.g. the log might have:

  request 1
  < notification 1
  < response 1

but we get:

> request 1
< response 1
< notification 1