To be able to implement L1, we need access to more information from
`BidiInfo`, namely `original_classes` of the `text`, in `visual_runs()`,
which would mean it should pass through `reorder_line()`.
The fact that information from `BidiInfo` is needed for both steps of
the public API (generating `BidiInfo` and consuming it
per-paragraph/per-level) made me change the API design and move these
methods into `impl BidiInfo`.
Then, since we needed access to `text` for every `BidiInfo` consumption,
I added a reference to `text` to `BidiInfo`, which also enables more
compile-time checks for `BidiInfo` isntance not outliving the text in
the user code.
NOTE: We are already breaking API in version 0.3.0 and paving for full
spec support is a good reason to do so, IMHO.
The L1 rule works by one pass on the text of the line.
Conformance Test: this implementation reduces the number of failures
from 60494 to 23770 (out of total 256747 cases).
Fix#2
Behnam Esfahbod