[move-function] Add support for loadable vars.
This is done by extending the support in the previous PR for
a. If we see the following pattern:
```
%0 = alloc_stack [lexical] $LoadableType, var
... *init of %0* ...
%1 = load [copy] %0 : $*LoadableType
%temporary = alloc_stack $LoadableType
store %1 to [init] %temporary : $*LoadableType
mark_unresolved_move_addr %temporary to %otherAddr : $*LoadableType
destroy_addr %temporary : $*LoadableType
```
we transform it to:
```
%0 = alloc_stack [lexical] $LoadableType, var
... *init of %0* ...
%1 = load [copy] %0 : $*LoadableType
%temporary = alloc_stack $LoadableType
store %2 to [init] %temporary : $*LoadableType
mark_unresolved_move_addr %0 to %otherAddr : $*LoadableType
destroy_addr %temporary : $*LoadableType
```
For safety reasons, we always make sure that %0 isn't destroyed in between
the load [copy] and the mark_unresolved_move_addr. After this runs, we can
use the address verifier on these types of vars with some additional work
that I am doing in a subsequent commit.
(cherry picked from commit 544b338baf0aacb4fe24115424384d688a9d6cdd)
