chore: Emit externalLinkInteracted events for buttons

[connorlanigan]

Description

We're already emitting the externalLinkInteracted in the Link component, when the external prop is enabled:

components/src/link/internal.tsx

Lines 72 to 109 in ea832bb

	const fireFunnelEvent = (funnelInteractionId: string) => {
	if (variant === 'info') {
	const stepName = getNameFromSelector(stepNameSelector);
	const subStepName = getNameFromSelector(subStepNameSelector);
	FunnelMetrics.helpPanelInteracted({
	funnelInteractionId,
	stepNumber,
	stepName,
	stepNameSelector,
	subStepSelector,
	subStepName,
	subStepNameSelector,
	elementSelector: getFunnelValueSelector(uniqueId),
	subStepAllSelector: getSubStepAllSelector(),
	});
	} else if (external) {
	const stepName = getNameFromSelector(stepNameSelector);
	const subStepName = getNameFromSelector(subStepNameSelector);
	FunnelMetrics.externalLinkInteracted({
	funnelInteractionId,
	stepNumber,
	stepName,
	stepNameSelector,
	subStepSelector,
	subStepName,
	subStepNameSelector,
	elementSelector: getFunnelValueSelector(uniqueId),
	subStepAllSelector: getSubStepAllSelector(),
	});
	}
	};
	const fireFollowEvent = (event: React.SyntheticEvent) => {
	if (funnelInteractionId) {
	fireFunnelEvent(funnelInteractionId);
	}

There are also instances where the Button component is used to build an external link. The Button component does not have an external prop, but it allows to set the iconName and target to replicate the behaviour.
When these properties are set, we will now send the same externalLinkInteracted event as in the Link component.

Related links, issue #, if available: n/a

How has this been tested?

Added unit test

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

---

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[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (85117c2) 93.47% compared to head (568a0be) 93.47%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1367   +/-   ##
=======================================
  Coverage   93.47%   93.47%           
=======================================
  Files         623      623           
  Lines       16769    16777    +8     
  Branches     5550     5551    +1     
=======================================
+ Hits        15674    15682    +8     
  Misses       1022     1022           
  Partials       73       73           

Files Changed	Coverage Δ
src/button/internal.tsx	100.00% <100.00%> (ø)

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[rubencarvalho]

Could we maybe add a test for when iconName="external" but no href is present?

[rubencarvalho]

LGTM, just left a comment about an additional test, to cover the case when isAnchor is false :)