Add `aria-expanded` and `aria-controls` attributes/functionality to va-button

[jerekshoe]

Bug Report

• [x] I’ve searched for any related issues and avoided creating a duplicate issue.
  • I found [this ticket]() that is similar, but was asked to create a separate ticket to track this bug

What happened

When attempting to add aria-expanded and aria-controls attributes to the button inside the va-button component, the attributes are not applied. These attributes are needed for screen readers

Chrome inspector

Element being inspected

What I expected to happen

I expected that the button in the shadow DOM would have the aria-expanded and aria-controls attributes so that screen readers could function properly when encountering this element

Urgency

How urgent is this request? Please select the appropriate option below and/or provide details

• [ ] This bug is blocking work currently in progress
• [x] This bug is affecting work currently in progress but we have a workaround
• [ ] This bug is blocking work planned within the next few sprints
• [ ] This bug is not blocking any work
• [ ] Other

Details

[caw310]

Hey team! Please add your planning poker estimate with Zenhub @Andrew565 @ataker @harshil1793 @it-harrison @jamigibbs @micahchiang @nickjg231 @powellkerry @rmessina1010 @rsmithadhoc

[jamigibbs]

I'm just adding a link to the Slack conversation about this design in case it will help us prioritize the work. It sounds like the usage of button in this design context may be removed or deprecated in the next few months.