Feature request: Improve visual_offset_from_block performance on long lines

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Steps to Reproduce

1. :open helix-term/src/commands.rs
2. % # select_all
3. <Alt-J> # join_selections_space
4. j # move_visual_line_down

Result

This hangs the UI for 30 seconds on my machine. Tracked it down to visual_offset_from_block with the following documentation:

/// Text is always wrapped at blocks, they usually correspond to
/// actual line breaks but for very long lines
/// softwrapping positions are estimated with an O(1) algorithm
/// to ensure consistent performance for large lines (currently unimplemented)

[pascalkuthe]

Do you have softwrap enabled? Otherwise that improvement won't do anything altough we may consider forcong softwrap for very long lines

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@pascalkuthe yes softwrap was enabled in this case