This commit ensures that even for requests that are known to be empty body
we at least attempt to read one bytes from the request body input stream.
This is done to work around the behavior in `sun.net.httpserver.ServerImpl.Dispatcher#handleEvent`
that will close a TCP/HTTP connection that does not have the `eof` flag (see `sun.net.httpserver.LeftOverInputStream#isEOF`)
set on its input stream. As far as I can tell the only way to set this flag is to do a read when there's no more bytes buffered.
This fixes the numerous connection closing issues because the `ServerImpl` stops closing connections that it thinks
weren't fully drained.

Also, I removed a now redundant drain loop in the Azure handler as well as removed the connection closing in the error handler's
drain action (this shouldn't have an effect but makes things more predictable/easier to reason about IMO).

I would suggest merging this and closing related issue after verifying that this fixes things on CI.

The way to locally reproduce the issues we're seeing in tests is to make the retry timings more aggressive in e.g. the azure tests
and move them to single digit values. This makes the retries happen quickly enough that they run into the async connecting closing
of allegedly non-eof connections by `ServerImpl` and produces the exact kinds of failures we're seeing currently.

Relates #49401, #49429

This commit ensures that even for requests that are known to be empty body
we at least attempt to read one bytes from the request body input stream.
This is done to work around the behavior in `sun.net.httpserver.ServerImpl.Dispatcher#handleEvent`
that will close a TCP/HTTP connection that does not have the `eof` flag (see `sun.net.httpserver.LeftOverInputStream#isEOF`)
set on its input stream. As far as I can tell the only way to set this flag is to do a read when there's no more bytes buffered.
This fixes the numerous connection closing issues because the `ServerImpl` stops closing connections that it thinks
weren't fully drained.

Also, I removed a now redundant drain loop in the Azure handler as well as removed the connection closing in the error handler's
drain action (this shouldn't have an effect but makes things more predictable/easier to reason about IMO).

I would suggest merging this and closing related issue after verifying that this fixes things on CI.

The way to locally reproduce the issues we're seeing in tests is to make the retry timings more aggressive in e.g. the azure tests
and move them to single digit values. This makes the retries happen quickly enough that they run into the async connecting closing
of allegedly non-eof connections by `ServerImpl` and produces the exact kinds of failures we're seeing currently.

Relates #49401, #49429

Same as #49518 pretty much but for GCS.
Fixing a few more spots where input stream can get closed
without being fully drained and adding assertions to make sure
it's always drained.
Moved the no-close stream wrapper to production code utilities since
there's a number of spots in production code where it's also useful
(will reuse it there in a follow-up).

Same as #49518 pretty much but for GCS.
Fixing a few more spots where input stream can get closed
without being fully drained and adding assertions to make sure
it's always drained.
Moved the no-close stream wrapper to production code utilities since
there's a number of spots in production code where it's also useful
(will reuse it there in a follow-up).

Same as #49518 pretty much but for GCS.
Fixing a few more spots where input stream can get closed
without being fully drained and adding assertions to make sure
it's always drained.
Moved the no-close stream wrapper to production code utilities since
there's a number of spots in production code where it's also useful
(will reuse it there in a follow-up).