Restructure persistence of remote workspaces to make room for WSL and other non-ssh remote projects (#36714)

This is another pure refactor, to prepare for adding direct WSL support.

###  Todo

* [x] Represent `paths` in the same way for all workspaces, instead of
having a completely separate SSH representation
* [x] Adjust sqlite tables
    * [x] `ssh_projects` -> `ssh_connections` (drop paths)
    * [x] `workspaces.local_paths` -> `paths`
    * [x] remove duplicate path columns on `workspaces`
* [x] Add migrations for backward-compatibility

Release Notes:

- N/A

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

Cargo.lock

@@ -19829,7 +19829,6 @@ dependencies = [
  "any_vec",
  "anyhow",
  "async-recursion",
- "bincode",
  "call",
  "client",
  "clock",
@@ -19848,6 +19847,7 @@ dependencies = [
  "node_runtime",
  "parking_lot",
  "postage",
+ "pretty_assertions",
  "project",
  "remote",
  "schemars",