Allow description and deprecated as a function with context

[fvieira]

While readOnly and hidden are able to react to other fields values through context, description and deprecated are static.
We often need to write description like:

description: `
Case 1: description for case 1
Case 2: description for case 2
`

while case 1 only occurs if the data is in one state and case 2 in another, and so we'd rather just show the right description according to the current data.
deprecated has the same issue, but worse, since even if we make the reason conditional, the
deprecated yellow text is always there.

What I'd like to have is this, just like on readOnly and hidden:

description: (context) => context.parent.someField === 'state1' ? 'description for case 1' : 'description for case 2'
deprecated: (context) => context.parent.someField === 'state1' ? {reason: 'some reason'} : undefined // (or false)