python3-urllib3: remove rust dependency

python3-urllib3: remove rust dependency

python3-cryptography (and thus, rust-native) is only needed by the
urllib3.contrib.pyopenssl module, which is not recommended for use up
the urllib3 upstream maintainers:

  Module for using pyOpenSSL as a TLS backend. This module was relevant
  before the standard library ssl module supported SNI, but now that
  we've dropped support for Python 2.7 all relevant Python versions
  support SNI so **this module is no longer recommended**.

Add a PACKAGECONFIG to control whether this module is shipped, and
disable it by default.

This removes rust-native from the default build of urllib3, which is in
the dependencies of other common modules such as requests and sphinx.

Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>