Fix local variables persisting in static functions

[NotHyper-474]

Fixes #277

This addresses a few things I've noticed:

• Checking locals in resolve is practically useless, since locals will have already been checked before hscript's expr calls it. I've debugged, and the only instance where locals were checked here was when they persisted due to a bug.
• Reverts the change of executeEx to exprReturn, seems like the bug that was fixed by it was subsequently resolved by a different change. This solves local variables persisting in static functions.
• Copies the fix from [BUGFIX] Fix locals getting dropped after calling script's own scriptCall #257 to apply it to static functions; solves static properties dropping local variables.

[NotHyper-474]

Also, the bug I'm talking about in the second point used to affect this repro script.

import funkin.modding.base.Object;

class StaticFunctionRepro extends Object
{
  public static function init():Void
  {
    var save = {version: "1.0"};
    var result = StaticFunctionRepro.checkSaveData(save);
    trace(result);
  }

  public static function checkSaveData(saveData:Dynamic):Dynamic
  {
    if (saveData.version != "2.0")
    {
      trace('Save data is outdated! Migrating...');
      saveData = migrateSaveData(saveData);
    }

    trace('Save data is good!');

    var updatedSaveData:Dynamic = getDefaultSaveData();
    return updatedSaveData;
  }

  public static function migrateSaveData(saveData:Dynamic):Dynamic
  {
    saveData.version = "2.0";
    return saveData;
  }

  public static function getDefaultSaveData():Dynamic
  {
    return {version: "2.0", other: true};
  }
}

After calling init, the local variables would act pretty weirdly, errors would be thrown as if they didn't exist. But now, even when replacing exprReturn with executeEx in the interp, which should've re-introduced the issue, it doesn't happen anymore.