Add expandable inline alert

[mcarrano]

Add expandable inline alert variant to Alert component. The user should be able to show/hide the contents of the alert by clicking the expansion caret.

patternfly/patternfly#4056

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[mcarrano]

@jessiehuff can you look at from an a11y perspective? Here is the design: https://marvelapp.com/prototype/9ihajjd/screen/79181732 Looks like this is limited to the inline version of the alert, although as you pointed out, that still can face the dynamic alert issue.

[jessiehuff]

I think that we'll likely just have to test this to make sure that focus shifts properly to the toggle and allows the user to expand the alert. I also think that it would probably require some documentation to explain the ways that this should and shouldn't be used. It also makes me wonder if this would be a good candidate to create a demo with. I think at one point we talked about creating a demo of an alert in a form, maybe this would fit into that?

[tlabaj]

closed by #6236