Migrate pygstc to asyncio based sockets.

[jameshilliard]

This should allow pygstc to be used properly in a non-blocking manner in addition to providing a cleaner abstraction over the TCP socket operations.

I also fixed the python tests to run properly in github actions.

[michaelgruner]

I love this. I'll review calmly next week. Thanks for your multiple submissions.

[jameshilliard]

I've rebased this however there's some failures unrelated to the changes in this pull request, I reworked the python test runner in #278 to fix the tests themselves(although some appear to still fail due to gstd bugs however).

[jameshilliard]

I've rebased this on top of #278 which fixes most tests.

[migueltaylor]

The main issue I see with this is that we currently support python >= 3.5. I could see migrating the client to python 3.6 but not to python 3.7 just yet. A lot of GstD users run it on NVIDIA JetPack and the latest version 4.6 still uses Ubuntu 18.04 and python 3.6. Unless there is an easy to maintain way to provide backwards compatibly I think we will have to wait a while to include this change.

[jameshilliard]

The main issue I see with this is that we currently support python >= 3.5.

Hmm, is it just NVIDIA JetPack using EOL python versions? 3.5 has been deprecated for a while now and 3.6 has been for a few months. This just updates the client library so I think if anyone need to use an older python they can just not install the new asyncio version probably right?

A lot of GstD users run it on NVIDIA JetPack and the latest version 4.6 still uses Ubuntu 18.04 and python 3.6. Unless there is an easy to maintain way to provide backwards compatibly I think we will have to wait a while to include this change.

Can't they just do apt install python3.7-dev? Seems to work fine for me on a normal ubuntu 18.04 system at least.

[TopperBG]

Keep in mind many Yocto projects, where change of packet, specialy Python is not as easy as apt install.