show_text tellraw hover events don't work for components that need resolving (nbt, score, selector)

The bug

The `show_text` hover event for the tellraw command doesn't work anymore for `nbt`, `selector` and `score`. This was fixed in MC-56373 and worked in both 20w17a and 20w18a and is broken since 20w19a.

How to reproduce

Both of the following hover events don't show the correct texts:

/tellraw @a {"text":"test","hoverEvent":{"action":"show_text","value":{"selector":"@s"}}}

/tellraw @a {"text":"test","hoverEvent":{"action":"show_text","contents":{"selector":"@s"}}}