[ublox] Do not run AT+COPS=0 when performing warm bootup if already registering/registered

[avtolstoy]

Problem

Despite being registered, an AT+COPS=0 call under some conditions may take substantial amount of time, which will prolong the bootup times.

Solution

1. Only perform AT+COPS=0 conditionally. This is only implemented for uBlox-based devices, as Quectel seems to behave correctly and also we cannot reliably tell whether it's attempting to perform registration or not (it may report +COPS: 0 even if it's not attempting to find an operator).
2. Additionally we've enabled packet domain errors (AT+CGEREP) which are useful in debugging connectivity issues
3. This PR also makes sure that failure to open muxer data channel used for PPP connections is treated as a non-recoverable failure, causing modem reset.

Steps to Test

1. Make sure a cellular device is connected to the cloud
2. Reset
3. AT+COPS=0 should not be executed
4. It should reconnect back to the cloud almost instantaneously without blocking for up to minutes in AT+COPS=0 despite being already registered

Example App

N/A

References

N/A

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Completeness

• User is totes amazing for contributing!
• Contributor has signed CLA (Info here)
• Problem and Solution clearly stated
• Run unit/integration/application tests on device
• Added documentation
• Added to CHANGELOG.md after merging (add links to docs and issues)

[keeramis]

One quick thought on this: As written in the attached AT manual, this will trigger a re-selection which we want to avoid for faster bootup times (which is all good). If we have to deal with roaming locations though, is it worth having an AT+COPS=0 setting to in fact trigger a re-selection because otherwise what if it doesn't attach to network as expected. Am I making sense? Should we have a check that tells when to set AT+COPS=0 and when not to set it? I know we have 10 min timeout, but even after 10min when we hit this line, looks like we won't do another AT+COPS=0 in case which we may not register on a given network with edge case roaming scenarios and such?

[avtolstoy]

But after 10 mins and a modem reset the modem on its own will start a new registration process (auto-COPS), right?

[keeramis]

Hmm.. good point. That's also right. It should. (Reset is supposed to be more powerful than anything else.)

[keeramis]

Please note the caveats that were discussed related to errors like 118 for Host is unreachable.
Log snippet:

0000098020 [lwip] TRACE: sent [IPCP ConfReq id=0x4 <addr 10.97.60.89> <msdns1 174.47.40.106> <msdns2 174.47.20.106>]
0000098023 [net.ppp.client] TRACE: TX: 29
0000098024 [lwip] TRACE: pppos_write[3]: len=26
0000099282 [net.ppp.client] TRACE: RX: 10
0000099284 [lwip] TRACE: pppos_input[3]: got 10 bytes
0000099286 [net.ppp.client] TRACE: RX: 28
0000099287 [lwip] TRACE: rcvd [IPCP ConfReq id=0x5]
0000099289 [lwip] TRACE: pppos_input[3]: got 28 bytes
0000099291 [net.ppp.ipcp] TRACE: input 4
0000099293 [lwip] TRACE: sent [IPCP ConfAck id=0x5]
0000099295 [net.ppp.client] TRACE: TX: 12
0000099296 [lwip] TRACE: pppos_write[3]: len=8
0000099298 [lwip] TRACE: rcvd [IPCP ConfAck id=0x4 <addr 10.97.60.89> <msdns1 174.47.40.106> <msdns2 174.47.20.106>]
.
.
0000100368 [lwip] TRACE: rcvd [IPCP ConfReq id=0x6]