Implement bundle reification

[kyouko-taiga]

The Emitter creates a call_bundle instruction when it sees a call to a method bundle. For example:

type A {
  public var x: Int
  public memberwise init
  public fun foo() -> Int {
    let { x.copy() }
    sink { x }
  }
}

public fun main() {
  _ = A(x: 42).foo()
}

The IR generated for call in main resembles the following (where %i0.1 is the address of some storage allocated for an A):

%i0.6: &A = access [let, sink] %i0.1
%i0.7: &Int = access [set] %i0.0
call_bundle [let, sink] @MethodDecl(2311)(%i0.6) to %i0.7
end_access %i0.7

We need a mandatory IR pass that will replace call_bundle by a simple call to the appropriate variant, depending on the strongest capability we may request on %i0.1. To determine what that is, we should look at all uses of %i0.1 after the definition of %i0.6. If there are none, then we can create an access [set] on the latter and call the sink variant of the bundle. Note that access reification will later collapse the sequence

%i0.6: &A = access [let, sink] %i0.1
%i0.x: &A = access [sink] %i0.6