Max length per line check

### Describe the problem

On multi-line strings it is not possible to check the maximum line length for each line.

For example when translating for displays that can show a certain amount of characters on multiple lines.

### Solution brainstorm

Add a `max-length-per-line:` check that splits the translation on line breaks and warns when any line is over the maximum length value.

### Describe alternatives you have considered

- Add a mode to the `max-length` check to switch between "full" and "line" mode: this would not allow having both checks active at the same time.

### Screenshots

_No response_

### Additional context

It should be clear what constitutes a line break is in each format.

Possibly related:
- #6987

Start by locating the existing max-length check and reviewing the discussion in issue #6987. Trace how each supported format defines line breaks, then determine how a separate max-length-per-line check should report overlong lines while remaining usable alongside the existing check.

Written by the indexing model from the issue text.