An optimizer for ARC (#14962)

* WIP: an optimizer for ARC
* do not optimize away destructors in 'finally' if unstructured control flow is involved
* optimized the optimizer
* minor code cleanup
* first steps to .cursor inference
* cursor inference: big steps to a working solution
* baby steps
* better .cursor inference
* new feature: expandArc for easy inspection of the AST after ARC transformations
* added topt_cursor test
* adapt tests
* cleanups, make tests green
* optimize common traversal patterns
* moved test case
* fixes .cursor inference so that npeg compiles once again
* cursor inference: more bugfixes

Co-authored-by: Clyybber <darkmine956@gmail.com>

tests/arc/topt_no_cursor.nim

@@ -0,0 +1,37 @@
+discard """
+  output: '''(repo: "", package: "meo", ext: "")'''
+  cmd: '''nim c --gc:arc --expandArc:newTarget --hint:Performance:off $file'''
+  nimout: '''--expandArc: newTarget
+
+var
+  splat
+  :tmp
+  :tmp_1
+  :tmp_2
+splat = splitFile(path)
+:tmp = splat.dir
+wasMoved(splat.dir)
+:tmp_1 = splat.name
+wasMoved(splat.name)
+:tmp_2 = splat.ext
+wasMoved(splat.ext)
+result = (
+  let blitTmp = :tmp
+  blitTmp,
+  let blitTmp_1 = :tmp_1
+  blitTmp_1,
+  let blitTmp_2 = :tmp_2
+  blitTmp_2)
+`=destroy`(splat)
+-- end of expandArc ------------------------'''
+"""
+
+import os
+
+type Target = tuple[repo, package, ext: string]
+
+proc newTarget*(path: string): Target =
+  let splat = path.splitFile
+  result = (repo: splat.dir, package: splat.name, ext: splat.ext)
+
+echo newTarget("meo")