Update RuntimeTypeMetadataUpdateHandler to be able to clear all caches

[stephentoub]

Contributes to #50938
cc: @mikem8361, @tommcdon, @pranavkm, @lambdageek

Note per our offline conversation, I changed the BeforeUpdate argument to be Type[] instead of Type.

[devsko]

Hi @stephentoub . Is my understanding correct that after

• adding a field to a Class in a loaded assembly via hot reload in a way very similar to what dotnet-watch does
• calling RuntimeTypeMetadataUpdateHandler.BeforeUpdate(null) via reflection
• calling typeof(Class).GetFields()

the added field should be in the result?
Because it isn't

[stephentoub]

@mikem8361, @tommcdon, the above will need investigation. The RuntimeTypeCache is correctly being cleared, and new methods and properties added with ApplyUpdate are correctly showing up via reflection after an update, but fields are not.

[devsko]

Thanks for looking into this