[tooltip] Fix shared tooltip closing with trigger gaps

[atomiks]

• I have followed (at least) the PR section of the contributing guide.

To reproduce: https://deploy-preview-3452--base-ui.netlify.app/react/components/tooltip#animating-the-tooltip

• Add gap: 30px (or whatever substantial value) between the triggers on the flex container
• Hover first trigger and wait for tooltip to open
• Hover to second trigger, then third
• Previously the tooltip would close when reaching the last trigger because the delay got reset back to the initial (due to the timeout not being cleared in a shared scenario.)

[pkg-pr-new]

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@3452
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@3452
  

commit: ac4e5c8

[mui-bot]

Bundle size report

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+186B(+0.05%)	🔺+45B(+0.03%)

Details of bundle changes

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