fix(compiler-core): generate the correct tree if comment is between if/else

[pikax]

fix #1256

Different approach than #1260

This parses the template as in dev, but strips the Comment nodes at the end, this ensures the whiteline removal still runs.

EDIT:

<div id="app">
	<div />
	<!-- loading -->
	<div />

	Hello
</div>

ouputs:

import { createVNode as _createVNode, createTextVNode as _createTextVNode, openBlock as _openBlock, createBlock as _createBlock } from "vue"

export function render(_ctx, _cache) {
  return (_openBlock(), _createBlock("div", { id: "app" }, [
    _createVNode("div"),
    _createVNode("div"),
    _createTextVNode(" Hello ")
  ]))
}

[yyx990803]

I did a similar fix in f3623e4 but should be more efficient to avoid double filtering calls.