Auto merge of #111858 - clubby789:fluent-alphabetical, r=jyn514,compiler-errors

Ensure Fluent messages are in alphabetical order

Fixes #111847

This adds a tidy check to ensure Fluent messages are in alphabetical order, as well as sorting all existing messages. I think the error could be worded better, would appreciate suggestions.

<details>
<summary>Script used to sort files</summary>

```py
import sys
import re

fn = sys.argv[1]
with open(fn, 'r') as f:
    data = f.read().split("\n")

chunks = []
cur = ""
for line in data:
    if re.match(r"^([a-zA-Z0-9_]+)\s*=\s*", line):
        chunks.append(cur)
        cur = ""
    cur += line + "\n"
chunks.append(cur)
chunks.sort()

with open(fn, 'w') as f:
    f.write(''.join(chunks).strip("\n\n") + "\n")
```
</details>

Author: bors