Move the initializer into the constructor for instance members that r… (#2867)

…eference identifiers declared in the constructor.

When TypeScript outputs modern language features, the below case throws
an TS error.

class C {
  a = this.x; // TS2729: Property 'x' is used before its initialization.

  constructor(public x:number){}
}
This error is fixed by moving the initializer of such class members into
the constructor.

This is a no-op change. This change came from Google.

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Co-authored-by: Barry Jaspan <[email protected]>
Co-authored-by: Andreas Arvidsson <[email protected]>

Author: 3 people