fix: compile incrementors in for loops within the initializer's flow

[CountBleck]

Fixes #2825.

Changes proposed in this pull request: ⯈ Compile for-loop incrementors within the initializer's flow

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[CountBleck]

@HerrCai0907 I don't think that's possible to do unless I have an assert in the incrementor. This should likely work just fine.

[HerrCai0907]

Like

function inc(i: i32): i32 {
  assert(i != 100); // failed
  return i + 1;
}

export function _start(): void {
  for (let i = 0; i < 1; i = inc(i)) {
    let i = 100;
  }
}