python3-cryptography: move from meta-python

* inherit new setuptools_rust class (which inherits new pyo3 class, which
  inherits cargo and python3-dir).
* RDEPENDS on python3-pytest-subtests for ptest
* Copy pyproject.toml for ptest as it defines the pytest.marker(s) needed
* Use 'cargo bitbake' to generate the crate:// SRC_URIs
   - Needed some hacks to the Cargo.toml in src/rust/ to make this work (probably
     only package.repository was strictly required):

     [package]
     description = "cryptography includes both high level recipes and low level interfaces to common cryptographic algorithms such as symmetric ciphers, message digests, and key derivation functions."
     homepage = "https://github.com/pyca/cryptography"
     repository = "https://github.com/pyca/cryptography"

* Add patches to src/rust/Cargo.toml to fix cargo errors including  pem version
* Add check-memfree.py to ptest to check for sufficient free memory

(From OE-Core rev: 27bd134c899d00d93806ecb0a62ec3f30b1e6ec6)

Signed-off-by: Tim Orling <tim.orling@konsulko.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-devtools/python/python3-cryptography/check-memfree.py

@@ -0,0 +1,10 @@
+#!/usr/bin/env python3
+# https://stackoverflow.com/questions/22102999/get-total-physical-memory-in-python/28161352
+import sys
+meminfo = dict((i.split()[0].rstrip(':'),int(i.split()[1])) for i in open('/proc/meminfo').readlines())
+mem_free = meminfo['MemTotal']/1024./1024.
+if mem_free < 2.:
+    raise RuntimeError("Insufficient free memory({:.3f}): requires > 2 GB".format(mem_free))
+    sys.exit(1)
+else:
+    print("Free memory: {:.3f} GB".format(mem_free))