Ensure end >= start in lsp::Range (#22690)

Should resolve https://github.com/zed-industries/zed/issues/21714.

In some conditions that I'm not sure of, Zed sends LSP requests with
`start > end` position, and zls has an [assertion for end >=
start](https://github.com/zigtools/zls/blob/f253553b8230ecd94824ecc3e2da2eb1643e7512/src/offsets.zig#L492),
and that causes zls to crash, like:

```bash
# first `textDocument/inlayHint` request with `end >= start`
[2025-01-05T19:33:09+00:00 TRACE lsp] outgoing message:{"jsonrpc":"2.0","id":1043,"method":"textDocument/inlayHint","params":{"textDocument":{"uri":"file:///Users/burak/Code/parzig/src/parquet/decoding.zig"},"range":{"start":{"line":0,"character":0},"end":{"line":24,"character":0}}}}
# successful response 
[2025-01-05T19:33:09+00:00 TRACE lsp::input_handler] incoming message: {"jsonrpc":"2.0","id":1043,"result":[{"position":{"line":0,"character":9},"label":": type","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":1,"character":22},"label":": type","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":4,"character":13},"label":": [](unknown type)","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":4,"character":30},"label":"T:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\ncomptime type\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":4,"character":33},"label":"n:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\nusize\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":5,"character":23},"label":": bool","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":6,"character":19},"label":": usize","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":9,"character":26},"label":": [](unknown type)","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":9,"character":43},"label":"T:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\ncomptime type\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":9,"character":47},"label":"n:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\nusize\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":21,"character":13},"label":": [](unknown type)","kind":1,"paddingLeft":false,"paddingRight":false},{"position":{"line":21,"character":30},"label":"T:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\ncomptime type\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":21,"character":33},"label":"n:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\nusize\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":22,"character":33},"label":"T:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\ncomptime type\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":22,"character":36},"label":"buf:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\n[]T\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":22,"character":41},"label":"bit_width:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\nu8\n```"},"paddingLeft":false,"paddingRight":true},{"position":{"line":22,"character":52},"label":"reader:","kind":2,"tooltip":{"kind":"markdown","value":"```zig\nanytype\n```"},"paddingLeft":false,"paddingRight":true}]}
[2025-01-05T19:33:09+00:00 TRACE lsp] Took 14.855ms to receive response to "textDocument/inlayHint" id 1043
# problematic `textDocument/inlayHint` request with `start > end`
[2025-01-05T19:33:09+00:00 TRACE lsp] outgoing message:{"jsonrpc":"2.0","id":1044,"method":"textDocument/inlayHint","params":{"textDocument":{"uri":"file:///Users/burak/Code/parzig/src/parquet/decoding.zig"},"range":{"start":{"line":50,"character":25},"end":{"line":25,"character":0}}}}
# zls crashes here, and after this point, all LSP requests fail
[2025-01-05T19:33:09+00:00 TRACE lsp] incoming stderr message:thread 5391652 panic: reached unreachable code
[2025-01-05T19:33:09+00:00 ERROR lsp] cannot read LSP message headers
```

In LSP specification for
[`Range`](https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#range)
type, it says:
> ... If you want to specify a range that contains a line including the
line ending character(s) then use an end position denoting the start of
the next line.

I feel like zls's assertion is sensible, so I've updated the generic
`range_to_lsp` function rather than doing something specific to zls. But
let me know if this seems incorrect.

zls was crashing after 5-10 minutes of working with a Zig codebase
before, and after this change, I tested for an hour and didn't
experience any crashes.

Release Notes:

- Ensure `end >= start` in `lsp::Range`, which should fix Zig/zls
crashes.

---------

Co-authored-by: Michael Sloan <michael@zed.dev>

crates/language/src/language.rs

@@ -1850,16 +1850,20 @@ pub fn point_from_lsp(point: lsp::Position) -> Unclipped<PointUtf16> {
 }
 
 pub fn range_to_lsp(range: Range<PointUtf16>) -> lsp::Range {
-    lsp::Range {
-        start: point_to_lsp(range.start),
-        end: point_to_lsp(range.end),
+    let mut start = point_to_lsp(range.start);
+    let mut end = point_to_lsp(range.end);
+    if start > end {
+        log::error!("range_to_lsp called with inverted range {start:?}-{end:?}");
+        mem::swap(&mut start, &mut end);
     }
+    lsp::Range { start, end }
 }
 
 pub fn range_from_lsp(range: lsp::Range) -> Range<Unclipped<PointUtf16>> {
     let mut start = point_from_lsp(range.start);
     let mut end = point_from_lsp(range.end);
     if start > end {
+        log::warn!("range_from_lsp called with inverted range {start:?}-{end:?}");
         mem::swap(&mut start, &mut end);
     }
     start..end