[Select] Pass rendered content of MenuItem to renderValue function

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Summary 💡

In the current situation it's possible to customize the rendered content of a Select component using the renderValue prop. This works really well I just have one gripe. I would like the rendered content of the selected MenuItem to be passed as an argument as well.

As a solution that wont break existing implementations I propose it would be passed as a second function argument, e.g.:

function(value: any, content: ReactNode) => ReactNode

When using the multiple prop the content argument would be an array of ReactNodes.

Motivation 🔦

Often I'm using customized content inside the MenuItems in my Select, like icons and avatars. When not using the renderValue prop this content is automatically rendered inside the Select when a selecting a value. However when using the renderValue prop you only get passed the value as function parameter, you would have to generate the content again inside the renderValue function.

Start by tracing the Select renderValue implementation and how selected MenuItem content is rendered. Confirm the existing renderValue(value) behavior, then verify that rendered content is available as a second argument and as an array for multiple selections without breaking existing usage.