Revert "JS: Make numeric union arms callable by adding a _ prefix"

[Shaptic]

This alleged fix is a product of a fundamental misunderstanding of the way that js-xdr works in terms of building the Union structures. In fact, this breaks them. The way that you can initialize numeric unions such as TransactionMeta, whose definition is:

union TransactionMeta switch (int v)
{
case 0:
    OperationMeta operations<>;
case 1:
    TransactionMetaV1 v1;
case 2:
    TransactionMetaV2 v2;
case 3:
    TransactionMetaV3 v3;
};

is by passing the enum switch and its value to the constructor, e.g.

  //   case 0:
  //       OperationMeta operations<>;
  //   case 1:
  //       TransactionMetaV1 v1;
  //   case 2:
  //       TransactionMetaV2 v2;
  //   case 3:
  //       TransactionMetaV3 v3;
  //   };

is by passing the enum switch and its value to the constructor, e.g.

const v3 = new xdr.TransactionMeta(3, new xdr.TransactionMetaV3({
  /* v3 parameters go here */
});

The "correct" way to fix this odd behavior is just by adding a constructor on the TypeScript side (i.e. in stellar/dts-xdr) as such:

class TransactionMeta {
  constructor(
    v: number, 
    value: 
      | xdr.TransactionMetaV1
      | xdr.TransactionMetaV2
      | xdr.TransactionMetaV3);
}