fix: Crashing due to input element hack (#36461)

This PR addresses a crash in text input element due to a hack to prevent
text input being trimmed.

The updated behavior will only add `zero width space` unicode character
to the node if there's no text content instead of adding it constantly.
Also by adding the same `zero width space` unicode character to text
area when there's no text content within will allow text area element to
properly display caret.

<img width="197" alt="截圖 2025-04-11 中午12 51 00"
src="https://github.com/user-attachments/assets/10bc7314-9aa3-49df-baac-ef26d39a96d8"
/>

This PR also addresses issues with multiple glyph runs:


https://github.com/user-attachments/assets/658db56f-b166-47ec-bc77-c6c13114d669

Testing: This PR is tested using:
- `./mach run -d 'data:text/html,<input id="input_element"
value="xxxxxxxxxxxxxxxxxxxx">'`
- `./mach run -d 'data:text/html,<textarea id="input_element"
value="xxxxxxxxxxxxxxxxxxxx">'`

without causing crashes, while the results should be covered by WPT
tests

Fixes: https://github.com/servo/servo/issues/36449

---------

Signed-off-by: DK Liao <dklassic@gmail.com>

components/layout_2020/flow/inline/text_run.rs

@@ -166,7 +166,7 @@ impl TextRunSegment {
                 self.bidi_level,
                 ServoRange::<ByteIndex>::new(
                     byte_processed + ByteIndex(self.range.start as isize),
-                    run.range.length(),
+                    ByteIndex(self.range.len() as isize) - byte_processed,
                 ),
             );
             byte_processed = byte_processed + run.range.length();