fixes #22672; Destructor not called for result when exception is thrown

[ringabout]

fixes #22672

Given a piece of code in a try statement:

let s = initMyObj("Hello world")

Before it was translated into (exits before the assignment)

var s
let tmp = initMyObj("Hello world")
if raised: goto end
s = tmp
end: 
destroy s

Now it exits after the assignment.

var s
let tmp = initMyObj("Hello world")
s = tmp
if raised: goto end
end:
destroy s

Tested locally

The first example

bin/nim c -d:useMalloc -r

==5698== LEAK SUMMARY:
==5698==    definitely lost: 0 bytes in 0 blocks
==5698==    indirectly lost: 0 bytes in 0 blocks
==5698==      possibly lost: 0 bytes in 0 blocks

the second and the third examples

Both of them keep a constant memory consumption (208)

[GC] total memory: 528384
[GC] occupied memory: 208

[GC] total memory: 528384
[GC] occupied memory: 208

[ringabout]

It seems that I need to find a way to properly destroy the tmp when raised. Work on it...