fix(Decimal128): throw error when passing a string to Decimal128 constructor

[vkarpov15]

You can get some nasty surprises when you pass a string to the Decimal128 constructor:

const bson = require('bson');

const v = new bson.Decimal128('14.92');

// {"$numberDecimal":"8.740930561E-6167"}
console.log(JSON.stringify(v));

Would be handy to at least throw an error. Although is there some reason why we can't just do fromString() if the user passes a string instead of a buffer to the Decimal128 constructor?

[vkarpov15]

Re: Automattic/mongoose#7815

[mbroadst]

I can't think of a reason we wouldn't support a string in the constructor, other than nobody thought to do it when they were originally implementing the module. How about adding that here with a test?

[daprahamian]

I'm on board with

function Decimal128(bytes) {
  if (typeof bytes === 'string') {
    return Decimal128.fromString(bytes);
  }
  this.bytes = bytes;
}

[agolin95]

https://jira.mongodb.org/browse/NODE-3018

[bajanam]

Thank you for submitting this PR! While our current development plan is at capacity, we will track this in Jira for future prioritization.