swift234

Support for stack promotion of array buffers in the stdlib.
The basic idea is to move the allocation of the buffer out of @_semantics("array.uninitialized") so that it can be inlined without inlining the semantics function (on high-level SIL).

This change in the stdlib also requires an adaption of the dead area elimination in DeadObjectElimination.
Otherwise it would just remove the semantics function but not the allocation and we would leak memory.