tl;dr: This adds `.block_mouse_except_scroll()` which should typically
be used instead of `.occlude()` for cases when the mouse shouldn't
interact with elements drawn below an element. The rationale for
treating scroll events differently:
* Mouse move / click / styles / tooltips are for elements the user is
interacting with directly.
* Mouse scroll events are about finding the current outer scroll
container.
Most use of `occlude` should probably be switched to this, but I figured
I'd derisk this change by minimizing behavior changes to just the 3 uses
of `block_mouse_except_scroll`.
GPUI changes:
* Added `InteractiveElement::block_mouse_except_scroll()`, and removes
`stop_mouse_events_except_scroll()`
* Added `Hitbox::should_handle_scroll()` to be used when handling scroll
wheel events.
* `Window::insert_hitbox` now takes `HitboxBehavior` instead of
`occlude: bool`.
- `false` for that bool is now `HitboxBehavior::Normal`.
- `true` for that bool is now `HitboxBehavior::BlockMouse`.
- The new mode is `HitboxBehavior::BlockMouseExceptScroll`.
* Removes `Default` impl for `HitboxId` since applications should not
manually create `HitboxId(0)`.
Release Notes:
- N/A