follow up #47471 

As described in #47471, we introduced a direction-aware strategy to
improve user experience when interacting with hover popovers. In this
follow-up, we are adding `hover_popover_sticky` and
`hover_popover_hiding_delay` to control whether the feature introduced
in 47471 enabled, and to let users configure the delay to balance
responsiveness . Also `hover_popover_sticky` can now be imported from
`editor.hover.sticky`, as well as `hover_popover_hiding_delay` from
`editor.hover.hidingDelay` in VSCode.


Also this PR adds several tests:
- `test_hover_popover_cancel_hide_on_rehover`: when the cursor returns
to the hover after leaving once within the hiding delay, the hover
should persist while canceling the existing hiding timer.
- `test_hover_popover_enabled_false_ignores_sticky` : when
`hover_popover_enabled` is false, the `hover_popover_sticky` and
`hover_popover_hiding_delay` have no effect(since no hover is shown).
- `test_hover_popover_sticky_delay_restarts_when_mouse_gets_closer`:
when mouse gets closer to hover popover, we expect the timer to reset
and the hover remains visible.
- `test_hover_popover_hiding_delay`: check if the delay(in test, that's
500ms) works.
- `test_hover_popover_sticky_disabled`: when hover_popover_sticky is
false, the hover popover disappears immediately after the cursor leaving
the codes.
- VSCode import test in `settings_store.rs`

Release Notes:

- Added `hover_popover_sticky` and `hover_popover_hiding_delay` settings
to balance responsiveness of hover popovers.

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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>