Fix parsing of nested class with constructor

[DimaIT]

Fixes the issue described below by remembering the HasConstructor flag and restoring it after parsing the class body.

---

Meriyah fails to parse the following code:

new class {
  start() {
    new class {
      constructor() {}
    }
  }

  constructor() {}          
}

Seems that the position of the outer constructor is what causes the problem cause when the outer constructor is above the start method Meriyah can parse it.

This snippet succeeds

new class {
  constructor() {}          

  start() {
    new class {
      constructor() {}
    }
  }
}

[3cp]

Thx!

[3cp]

It lets me to think: to deal with similar nested situations, a stack of flags/context might be better.

[3cp]

There are some minor issues in unit tests to be fixed, missing "decorators": [] in various places.

[DimaIT]

There are some minor issues in unit tests to be fixed, missing "decorators": [] in various places.

Fixed and added a couple more tests.

[3cp]

Thx!
v4.3.7 is released.