fix(popover): ensure popover does not go offscreen when adjusting top position

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
  • Some docs updates need to be made in the ionic-docs repo, in a separate PR. See the contributing guide for details.
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Issue URL: resolves #25349

What is the new behavior?

• When adjusting the top position of the popover, call Math.max so that the position is next < 0. The trade off here is that the popover may not perfectly align with the coordinates of the trigger. However, the alternative here would be to keep the popover below the trigger and have the browser resize the popover to be really small (which does not seem very useful).

Does this introduce a breaking change?

• Yes
• No

Other information

[averyjohnston]

Now the popover always opens in the same spot, instead of at your mouse cursor; was that intentional?

[liamdebeasi]

Should be fixed now