fix: require hat select before ready up (#1037)

Fixes #963

## Changes

-
[6781542](6781542)
`PlayerSlot` is now (sort of) a state machine, starting out `Empty` then
progressing through `SelectingPlayer` and `SelectingHat` until becoming
`Ready`
- Slot for a network player only uses the `SelectingHat` and `Ready`
states for simplicity
- Angled brackets `<` and `>` show around the thing being selected
(player/hat), brackets now don't show when ready
-
[a2393c4](a2393c4)
fix bug where label has incorrect text for 1 frame when pressing Menu
Back to remove player from slot
-
[f636d33](f636d33)
Upgrade bones to latest
- Set gitattributes for `*.ftl` files so that they are treated as text
for diffs and not binary files
- Ignore advisory `RUSTSEC-2024-0370` proc-macro-error is unmaintained
(see [related bones issue](fishfolk/bones#479)
and [the advisory](https://rustsec.org/advisories/RUSTSEC-2024-0370))

This also fixes a bug I was seeing on `main` where another player in a
LAN lobby pressing A/D would behave as if everyone pressed A/D, e.g.
pressing D to select the next skin would change to the next skin in both
slots.

**Rationale for the rough state machine:**

Previously there were 3 states for a player slot: Empty,
SelectingPlayer, and Ready + SelectingHat. This state was maintained by
two booleans, `active` and `confirmed`, which tell you whether the slot
is not empty and whether the player has readied-up respectively.
Together they represent the 3 states as: (`active/confirmed`)
`false/false`, `true/false` and `true/true`; with `false/true` being an
invalid state.

Now that there are four states to the ready-up process, one way of
implementing this is to add a third boolean, but this introduces 3 more
invalid states. Let's say the boolean is called `selectedPlayer`, these
are the possible boolean combinations and the states they represent
(`active/selectedPlayer/confirmed`):

```
false/false/false Empty
false/false/true <invalid>
false/true/false <invalid>
false/true/true <invalid>
true/false/false SelectingPlayer
true/false/true <invalid>
true/true/false SelectingHat
true/true/true Ready
```

The implementation I opted for is a simple state machine. While it added
a lot more code to some areas of this module I found it made reasoning
about some sections much easier. It also made explicit certain edge
cases in the `handle_match_setup_messages` system where e.g the client
could theoretically receive a confirmation message from a peer when it
had not yet received any player selection messages. A warning log is now
generated in the unlikely case this occurs.

.gitattributes

@@ -21,5 +21,7 @@ web/* linguist-vendored
 assets/** binary
 old_assets/** binary
 
+*.ftl diff
+
 # If you have other directories with mostly binary files, add them like this:
 # other_binary_directory/** binary