1. Postpone the computation of the signature for property
reference getters for extension properties until codegen time.
2. Generate metadata for static replacement functions instead
of the original functions.
This is possible now because after 3a9b94235f, 0423d0f41e and
5341de253f, all top level functions/properties in sources and in
binaries have a corresponding containing facade class
Getter of a primary value of an inline class belongs to the box class.
Its arguments should not be unboxed when the method is called.
However, its result might require boxing if it's an inline class value.
When we have an internal primary value, there's no getter method.
In fact, we can use box/unbox methods for inline class directly
(don't forget to box the result, it may be an inline class type value).
#KT-26748
