Previously, HttpComponents5MessageSender can be configured to use both
a custom HttpClient or configure one using a number of convenient
properties. This setup creates an odd arrangement where calling those
convenient methods once an HttpClient is set throws an exception as
the implementation supports one or the other.
This commit moves the first use case in a simple implementation that
only accepts a custom HttpClient or the state of
HttpComponents5ClientFactory for convenience and discoverability.
Specifying an HttpComponents5MessageSender is deprecated as a result.
Closes gh-1519
f250abb0cf