Refine line breaking around graphemes and grapheme clusters

Nobody has claimed this yet.

CRLF is treated as two line breaks, [though it should be treated as one](https://www.unicode.org/reports/tr13/tr13-9.html#Interpreting_characters_in_text:~:text=on%20input%20and%20in%20interpretation%2C%20treat%20CR%2C%20LF%2C%20CRLF%2C%20and%20NEL%20the%20same). In this case, we'd want to break around the whole grapheme cluster `\r\n`.

Using `examples/vello_cpu_render/src/main.rs`:

```rust
let text = String::from(
"Start\nSome text here. Let's make it a bit longer so that line wrapping kicks in 😊. And also some اللغة العربية arabic text.\r\nThis is underlining pq and strikethrough t",
);
```

```rust
let text = String::from(
"Start\r\nSome text here. Let's make it a bit longer so that line wrapping kicks in 😊. And also some اللغة العربية arabic text.\r\nThis is underlining pq and strikethrough t",
);
```

However, for ligatures, which form a single grapheme cluster, we still need to wrap on characters, e.g if layout width is 1px:
Current behaviour:

Expected:

Start with examples/vello_cpu_render/src/main.rs and reproduce the two CRLF cases and the 1px ligature case. Trace the line-breaking and grapheme-cluster handling used by the example; done means CRLF breaks as one cluster while ligatures can still wrap between characters at very narrow widths.

Written by the indexing model from the issue text.