Dropdown component doesn't support component label.

[Kimi1020]

Title line template: [Title]: Brief description

I want to show the component label after selecting a component option for dropdown.

What package(s) are you using?

carbon-components-react

Detailed description

Describe in detail the issue you're having. Is this a feature request (new
component, new icon), a bug, or a general issue?

Is this issue related to a specific component?
Yes, carbon/packages/react/src/components/Dropdown/Dropdown.js

What did you expect to happen? What happened instead? What would you like to
see changed?
For dropdown component, if I use itemsToElement to make option an component, after select it, it will show itemToString function's result. I think it should show the component as well.

After I checked the source code of Dropdown.js, I found below code. It use itemToString function to render the label. In my circumstance, I want to use itemToElement to render the label. Shall we support it for this dropdown component?

{selectedItem ? itemToString(selectedItem) : label}
Source: carbon/packages/react/src/components/Dropdown/Dropdown.js

What browser are you working in?
chrome v79
What version of the Carbon Design System are you using?
carbon-components-react": "^7.7.3"

[Kimi1020]

If I set itemToString={itemToElement}, below key={itemToString(item)} will report object key warning.
<ListBox.MenuItem key={itemToString(item)} isActive={selectedItem === item} isHighlighted={ highlightedIndex === index || selectedItem === item } {...getItemProps({ item, index })}> {itemToElement ? ( <ItemToElement key={itemToString(item)} {...item} /> ) : ( itemToString(item) )} </ListBox.MenuItem>

[jendowns]

I can help with this 👍 PR coming shortly

UPDATE: PR is here #4977