feat: implement an async iterable request class

[chdh]

This PR implements an async iterable request class.

The new class IterableRequest is implemented as a super class of the normal Request class. It is an AsyncIterable providing an AsyncIterator and can be used with for await.

Usage:

const request = new IterableRequest("select 42, 'hello world'");
connection.execSql(request);
for await (const item of request) {
  console.log(item.row);
}

A unit test is included. The API documentation has yet to be written.

Implements #1550

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 83.69565% with 15 lines in your changes missing coverage. Please review.

Project coverage is 78.39%. Comparing base (65ab37d) to head (9691e11). Report is 16 commits behind head on master.

Files with missing lines	Patch %	Lines
src/iterable-request.ts	83.69%	9 Missing and 6 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1644      +/-   ##
==========================================
- Coverage   79.01%   78.39%   -0.63%     
==========================================
  Files          93       91       -2     
  Lines        4876     4947      +71     
  Branches      937      948      +11     
==========================================
+ Hits         3853     3878      +25     
- Misses        720      768      +48     
+ Partials      303      301       -2     

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[arthurschreiber]

First of all, this is super exciting - thank you for working on this! ❤️

I haven't taken a super deep look into the implementation yet, but my idea for this was always to change the API for request execution to something like this:

// Create a new request, but without callback.
const request = new Request('select a, b, c from foobar');

// `using` so any resources are free'd to make the connection reusable in case some error happens in the user's code
using response = await connection.execSql(request);

// `.values` for a rows as arrays
// `.objects` for rows as objects
for await (const [a, b, c] of response.values()) {
  ...
}

Obviously, making such a profound change to the API is not simple, and there's going to be a lot of concerns around backwards compatibility and things like that.