fix(tooltips): fix arrow position when using end-bottom placement

[ze-flo]

Description

Fixes a regression created in #1882

Detail

• Refines defaultInset to better render on retina and regular monitors
• Adds ability to shift the arrow placement alongside the edge of the parent container. This addresses the case when a parent container is too short for be supported by the default arrow placement logic.

For example:

The arrow of a small tooltip using end-bottom placement will extend past the container's boundaries because of the border-radius

Before

After

Checklist

• 👌 design updates will be Garden Designer approved (add the designer as a reviewer)
• 🌐 demo is up-to-date (npm start)
• ~~:arrow_left: renders as expected with reversed (RTL) direction
• ⚫ renders as expected in dark mode
• ~:metal: renders as expected with Bedrock CSS (?bedrock)~~
• 💂‍♂️ includes new unit tests. Maintain existing coverage (always >= 96%)
• ~~:wheelchair: tested for WCAG 2.1 AA accessibility compliance
• 📝 tested in Chrome, Firefox, Safari, and Edge

[jzempel]

Suggested change

	arrowSize = margin;
	if (['left-start', 'left-end', 'right-start', 'right-end'].includes(placement)) {
	arrowShift = '-4px';
	}
	if (['left-start', 'left-end', 'right-start', 'right-end'].includes(placement)) {
	arrowShift = '-4px';
	} else {
	arrowShift = margin;
	}

[nit] prefer clarifying assignment

[jzempel]

Would it be better to tie this to the theme with

arrowShift = `-${theme.borderRadii.md}`;

to better indicate the shifting rationale and respond to theming customizations that knock out the borders?

[geotrev]

Nice!