Expandable section - update to use <Button> for toggle

[mcoker]

Follow up to core PR - patternfly/patternfly#7000

TL;DR of the updates:

• Replace the custom button in expandableToggle with a <Button variant="link">
  • Move all of the logic that was on the custom button to the new <Button>
• Wrap the expandableToggle in <div className={css(styles.expandableSectionToggle)}>

Some more details:

• We want to pass the span.expandableSectionToggleIcon (the span with the toggle icon class and icon inside, as it is currently) in as the <Button>'s icon. This whole thing:

  patternfly-react/packages/react-core/src/components/ExpandableSection/ExpandableSection.tsx

  Lines 240 to 242 in 2e6837e

  	<span className={css(styles.expandableSectionToggleIcon)}>
  	<AngleRightIcon aria-hidden />
  	</span>

• The <Button> should have isInline if the "truncate" variant is used on <ExpandableSection> (expandableSectionVariant.truncate)
• Here is the logic on the expandable section's button in core in case it's helpful https://github.com/patternfly/patternfly/blob/3234848901d1bfe0c632445d7d93088e87b098d7/src/patternfly/components/ExpandableSection/expandable-section-toggle.hbs#L5-L18