Don't update the text buffer in text_system

[ickshonpe]

Objective

Text is shaped in measure_text_system. When the schedule reaches text_system there's no need to reupdate the cosmic-text buffer a second time. text_system should only be updating any stale TextLayoutInfo components.

Solution

• Add a new method update_text_layout_info to TextPipeline. This method updates the given TextLayoutInfo without performing any shaping.
• Call update_text_layout_info instead of queue_text from text_system.
• Only query for TextFont, instead of the full TextUiReader.

There are some more changes that seem desirable, the glyph info updates should probably be done in measure_system for instance, but I'll leave those for followup PRs.

Testing

yellow = this PR, red = main

cargo run --example many_glyphs --release --features trace_tracy,debug -- --no-text2d --recompute-text

cargo run --example many_buttons --release --features trace_tracy,debug -- --text --respawn