Revert broken asynchttpserver FutureStream additions.

[dom96]

As discussed in #13394, these changes cannot work. Reverted via

git revert --no-commit 5bf571f061d53d35aab727f420afd9f415987723
git revert --no-commit abd660c407d00d0c4f2129ff11bfc69badda8ece
git revert --no-commit 955465e5f42b1353f69f3bd884908a7ef91ce13b
git commit

[Araq]

Pinq @mrhdias. As I said elsewhere, better than reverting this is fixing the feature so that it works well. It's an important feature.

[mrhdias]

Pinq @mrhdias. As I said elsewhere, better than reverting this is fixing the feature so that it works well. It's an important feature.

Thank you @Araq. The idea of using an iterator is not new.
#6576

I replace "let data = request.client.recv(readSize)" with "let data = waitFor request.client.recv(readSize)" to wait for the data.

So, reading the data is clear:

for data in req.bodyStream(8*1024):
  echo data

Iterator code

when (NimMajor, NimMinor) >= (1, 0):
  iterator bodyStream*(
    request: Request,
    chunkSize: int = 8*1024): string =
    ## The chunkSize parameter is optional and default value is 8*1024 bytes.
    ##
    ## This iterator return a tuple with the length of the data that was read
    ## and a future.
    var remainder = request.contentLength
    while remainder > 0:
      let readSize = min(remainder, chunkSize)
      let data = waitFor request.client.recv(readSize)
      if data.len != readSize:
        raise newException(ValueError, "Error reading POST data from client.")
      yield data
      remainder -= readSize

[mrhdias]

Another solution forum (Thanks Hlaaftana): https://forum.nim-lang.org/t/5971

template forStream(req: Request, chunkSize: int, name, body: untyped): untyped =
  var remainder = req.contentLength
  while true:
    let `name` = await req.client.recv(min(remainder, chunkSize))
    body
    remainder -= len(`name`)
    if remainder == 0:
      break

req.forStream(8*1024, d):
  echo d

[dom96]

It is better to fix this, but it's going to be much easier to review if we start fresh IMO. Can we merge this?

[dom96]

Okay, I am merging this since there was no feedback in 12 days. Please ping me to review any new PRs on this.