NetServices: format code using `haiku-format`

This commit formats all the netservices2 code with the `haiku-format` tool from
https://github.com/owenca/haiku-format (commit aa7408e), with the following
customizations:
* SpaceBeforeRangeBasedForLoopColon is set to false
* Braces before a catch block are not wrapped
* Most headers, except for ExclusiveBorrow.h, have been manually reformatted
to adhere to Haiku's header format (issue #19 in the repository)

Change-Id: I693c4515cf26402e48f35d1213ab6d5fcf14bd1e

NetServices: Add debugging constants and messages

These allow for additional messages about the progress/status of the request.
For now, the messages are sent unconditionally, though it may be reasonable to
in the future switch to sending them only when enabled.

Change-Id: Ic45a0055037af02c689494fa5ce0acd03592ad7e

NetServices: Add custom error message to BNetworkRequestError

Change-Id: I03970762531a689e25cd78a1091aecf755ee87ce

NetServices: Implement asynchronous status update messages.

The integration PostTest has a basic test that the expected messages are sent and
have the expected data fields. The gist is documented in book.dox.

To do are the messages around SSL. However, that functionality is also not
implemented yet, so there is nothing to send.

Change-Id: Ib8f36ed32f9854d643d8256338b71af7067059f0

NetServices: Add support for Basic authentication

Change-Id: I304104f7096fd935212e1bfa3e988e7945cb5cec

NetServices: Add the BNetworkRequestError type

This is a generic error type that can be used by multiple protocols to describe errors that can
occur while processing a request. The error type supports adding an additional error code in cases
where there is an underlying system error.

The type will be used to describe errors that occur while processing requests by BHttpSession, and
it is generally going to be thrown by the receiving BHttpResult.

Change-Id: I76c0bbaedd38df8cfb79159c4beae2fbf1350aab

NetServices: Add skeleton BHttpSession class and its documentation

Change-Id: Ia8a35588422908f6fe9b839ce239fb478baf298b