Self-bound types produced with the `index<>` type function and `typeof` being used recursively, crashing the new solver

[nothing1649]

As of version 0.658, the following two cases crash the new solver, regardless of strict mode being used. Due to typeof being used recursively this should produce a type error instead, however it crashes instead:

--!strict
local propertyKeys:{propertyKey} = nil::never
--InternalCompilerError - ConstraintSolver::unblock encountered a self-bound type!
type propertyKey = index<typeof(propertyKeys), number>

Changing the case slightly results in a different error (possibly the same underlying cause?):

--!strict
--InternalCompilerError - Luau::follow detected a Type cycle!!
local propertyKeys:{propertyKey} = nil::never
type propertyKey = index<typeof(propertyKeys), number>
local propertyKey:propertyKey = propertyKeys
if propertyKey then end