extmod/modtls: Move the native ssl module to tls.

The current `ssl` module has quite a few differences to the CPython
implementation.  This change moves the MicroPython variant to a new `tls`
module and provides a wrapper module for `ssl` (in micropython-lib).

Users who only rely on implemented comparible behavior can continue to use
`ssl`, while users that rely on non-compatible behavior should switch to
`tls`.  Then we can make the facade in `ssl` more strictly adhere to
CPython.

Signed-off-by: Felix Dörre <felix@dogcraft.de>

tests/extmod/tls_sslcontext_micropython.py

@@ -0,0 +1,29 @@
+# Test MicroPython-specific behaviour of tls.SSLContext.
+
+try:
+    import tls
+except ImportError:
+    print("SKIP")
+    raise SystemExit
+
+# Test constructing without any arguments (in CPython it's a DeprecationWarning).
+try:
+    tls.SSLContext()
+except TypeError:
+    print("TypeError")
+
+# Test attributes that don't exist (in CPython new attributes can be added).
+# This test is needed for coverage because SSLContext implements a custom attr handler.
+ctx = tls.SSLContext(tls.PROTOCOL_TLS_CLIENT)
+try:
+    ctx.does_not_exist
+except AttributeError:
+    print("AttributeError on load")
+try:
+    ctx.does_not_exist = None
+except AttributeError:
+    print("AttributeError on store")
+try:
+    del ctx.does_not_exist
+except AttributeError:
+    print("AttributeError on delete")