Edge gateway connection broken but shows as connected

[richturner]

Describe the bug
If the TCP WS connection gets broken between the edge gateway and the central instance then the edge gateway is unaware and still shows as connected and never enters the reconnect logic.

To Reproduce
Steps to reproduce the behavior:

1. Setup an edge gateway and central instance
2. Once edge gateway is connected restart the central manager container
3. Edge gateway manager interconnect UI will still show as connected but central manager gateway status will be disconnected

Expected behavior
Edge gateway should detect broken pipe and enter reconnect logic.

[richturner]

Should introduce a WS ping pong and check keep alive / timeout config.