support for union types in struct104

Fixed parameter named from lowercase to CameCase in statemachine.install.

use the correct field serializer for the Encoding field by looking up field type instead of hardcoded 'Byte'

__bytes__ on the Buffer object is sometimes returning a bytearray instead of bytes.

Traceback (most recent call last):
  File "C:\Users\ddeason\PycharmProjects\opcua_test\venv\lib\site-packages\asyncua\client\ua_client.py", line 88, in _process_received_data
    data = bytes(buf)
TypeError: __bytes__ returned non-bytes (type bytearray)

* added fixmes about types
* added type hinting

* added cast to Index
* added fixmes about wrong type hinting in uaprotocol_auto.py

This commit closes #752.

With py3.10, high level asyncio API can't specify the event_loop
argument anymore.

Consequently When using thread dedicated to run the event_.loop, we now need to
instantiate object like asyncio.Lock within the thread. However, the
event loop can't be running before creating these objects as
`loop.run_for_ever()` must be the background running thread process.
Therefore we can't have "get_running_loop()" calls in object
constructors (like HaClient)
when used with executors.

Before
```
In [15]: def get_t():
    ...:     loop = asyncio.new_event_loop()
    ...:     t = T()
    ...:     loop.run_for_ever()

In [16]: class T:
    ...:     def __init__(self, loop):
    ...:         asyncio.set_event_loop(loop)
    ...:         asyncio.get_running_loop()
    ...:         self.l = asyncio.Lock()
    ...:         print("Lock created")
    ...:

In [17]: t = Thread(target=get_t);t.start()

Exception in thread Thread-9:
Traceback (most recent call last):
  File "/usr/local/lib/python3.8/threading.py", line 932, in _bootstrap_inner
In [41]:     self.run()
  File "/usr/local//lib/python3.8/threading.py", line 870, in run
In [41]:     self._target(*self._args, **self._kwargs)
  File "<ipython-input-32-c4a1ea4cfdac>", line 3, in get_t
  File "<ipython-input-39-ebeae10dd173>", line 4, in __init__
RuntimeError: no running event loop
```
After

```
In [15]: def get_t():
    ...:     loop = asyncio.new_event_loop()
    ...:     t = T()
    ...:     loop.run_for_ever()

In [16]: class T:
    ...:     def __init__(self, loop):
    ...:         asyncio.set_event_loop(loop)
    ...:         self.l = asyncio.Lock()
    ...:         print("Lock created")
    ...:

In [17]: t = Thread(target=get_t);t.start()

Lock created

```

This reverts commit 49fefd4d.

fix add properties/variables in _create_custom_type

* Update xmlimporter.py

This allows to load information about newly created data types in the same import process

* Update xmlparser.py

with this we can set the value to newly created datatypes

* Update ua_utils.py

This is conform to the I40AAS nodeset enumerations, e.g. given enumeration as "AccessPermissionRule_0" specifying the type and the integer

* Update xmlimporter.py

small changes due to necessary async and await

* Update xmlparser.py

switched from try/catch to check