Add sync_wrapper functions

[okapies]

Add sync_uaclient_method and sync_async_client_method to use the underlying asynchronous methods while leveraging sync.Client.

[oroulet]

What issue does that code fix? I am a bit in a hurry but I could not understand.

[okapies]

Some functionalities of the async client (both Client and UaClient) are not implemented in the sync client. I want to use them directly combined with the thread loop run in the sync Client.

[oroulet]

we can have that method in addition, but why not adding the missing methods in the sync client?

[okapies]

Thanks for the merge. Because I finally found that I need to use UaClient directly for my use cases (e.g., handling detailed statuses for each item from the OPC server while reading values) in addition to #1369 and #1370.