Create an integration test for c8y-remote-access-plugin

[Bravo555]

When making a change to c8y-remote-access-plugin to remove webpki dependency in #2185, a regression was manually caught. To reproduce:

1. feature tokio-rustls-native-certs was disabled which resulted in TLS support being disabled
2. Modified c8y-remote-access-plugin replaced the original binary in /usr/bin/c8y-remote-access-plugin
3. Initiate a remote connection from Cumulocity. Any parameters should trigger the error, but what I used was:
   • Protocol: SSH
   • Sign-in method: Username and password
   • Host: 127.0.0.1
   • Port: 22

Expected: Remote connection is successfully created, prompt is displayed and one can invoke commands.

Observed:

• remote access terminal window printed the following message:

  Device disconnected.  
  
  Websocket connection was closed.

• the following was published on the MQTT broker:

[c8y/s/us] 502,c8y_RemoteAccessConnect,"

Error:   × Connecting to Websocket
  ├─▶ URL error: TLS support not compiled in
  ╰─▶ TLS support not compiled in

"

This seems like it could be easily caught by an automated integration test, but no such test existed for c8y-remote-access-plugin, so it should be created.

The challenging portion is that remote connections are initiated by Cumulocity and the plugin needs to verify Cumulocity's TLS certificate.

[reubenmiller]

Add system tests has been added in https://github.com/thin-edge/thin-edge.io/pull/3006 to verify a successful connection to a device via the Cumulocity IoT Cloud Remote Access feature

[gligorisaev]

QA has thoroughly checked the feature and here are the results:

• [x] Test for ticket exists in the test suite.
• [x] QA has tested the function and it's functioning according