[mlir][EmitC]Expand the MemRefToEmitC pass - Adding scalars (#148055)
This aims to expand the the MemRefToEmitC pass so that it can accept
global scalars.
From:
```
memref.global "private" constant @__constant_xi32 : memref<i32> = dense<-1>
func.func @globals() {
memref.get_global @__constant_xi32 : memref<i32>
}
```
To:
```
emitc.global static const @__constant_xi32 : i32 = -1
emitc.func @globals() {
%0 = get_global @__constant_xi32 : !emitc.lvalue<i32>
%1 = apply "&"(%0) : (!emitc.lvalue<i32>) -> !emitc.ptr<i32>
return
}
```