Modify network detection on QNX to delay SD

[kheaactua]

Overview

Introducing a simple_connector to mimic the netlink_connector (in a very limited way) on QNX. This PR is not intended to be merged upstream, but instead serves as a discussion topic and example.

Description

Implemented a "simple_connector" to mimic the netlink_connector available on Linux. This connector, along with vsomeip3.5.4 introduction of the RS_DELAYED_RESUME routing state, allows us to delay SD until the network is available.

The simple_connector works by using QNX's waitfor to wait for a file whose creation indicates network availability. This file is created externally.

The simple_connector does not continue to monitor the network. It simply notifies the routing_manager the first time the network is available.

That said, the interface does allow for easy extension in the future

This behaviour is controlled with the env vars VSOMEIP_USE_ASYNCHRONOUS_SD and VSOMEIP_WAIT_FOR_INTERFACE.

An alternative implementation would be to use PPS, but that isn't available by default on our deployment of QNX 7.

This implementation has a reduced foot print from earlier implementations and also does not modify any interfaces.

Notes

• There is no timeout on the waitfor. The original implementation had a configurable timeout, however because timing out left us in an error state anyways, this timeout was removed (raised to numeric_limits<int>::max() = ~45 days, give or take.)
• This capability was previously implemented in https://github.com/COVESA/vsomeip/pull/710 for 3.4.10, however that change had a huge footprint and fundamentally altered the startup process making it hard to maintain