Stream repo zip/tar.gz/bundle achives by default

[silverwind]

Feature Description

A common problem that users report is their disk running out of space because of all the repo archive "caches". I propose a new option repository.STREAM_ARCHIVES which by default would be enabled and which will directly stream the compressed bytestream to the client, which will:

1. Improve initial download performance as the POST+GET negotiation on UI goes away and it will be pure GET.
2. Reduce performance on subsequent downloads, because there is no cache anymore, but busy instances with enough disk space can opt into cache by disabling the option.
3. Eliminate any worries regard the disk running out of space.
4. Prevent the client from showing download progress because content-length will not be communicated to the client for streamed downloads.