Improve the selection/hover behavior for plots

[jleibs]

What

• Resolves: Double clicking plot background selects the first series #5090

Several changes to plots:

• When resetting the plot, don't trigger a selection. Previously if an item ended up under the cursor after the reset, it would end up selected.
• Additionally, when hovering/clicking the background of the plot, process hover/selection accordingly.

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG
• If applicable, add a new check to the release checklist!

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[Wumpf]

very nice, great test protocol

[teh-cmc]

I'd go one step further and add a bullet point for pressing escape now that #5103 is in

[Wumpf]

ah shoot saw your comment too late @teh-cmc !

[teh-cmc]

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