Implement Silicon Labs EFR32 Wi-SUN support

[ismilak]

Significant features and modifications:

• Implementing EFR32 OSAL port
• Refactoring build targets to standardise the build process and the output
• Implementing Vendors/Silabs context
• New config file interface for Sample Application to set the NMS and Agent parameters compile time
• New portable TLV getter/setter interface to support multiple platforms
• Specialised TLVs for EFR32 Wi-SUN platform: IPv6 address and some Vendor data
• Removing select API usage in CoAP Client/Server, since it operates with only one socket descriptor
• Implementing bi-directional integration solution: Csmp Agent lib into Silicon Labs SDK and Silicon Labs SDK into Cisco Csmp Agent repository to support both build systems
• Updating readme files with EFR32 Wi-SUN content

[ismilak]

Tested all targets on all possible platforms:

• Ubuntu 22.04: linux, freertos, efr32_wisun
• Windows10: efr32_wisun
• MacOS: linux, freertos, efr32_wisun (for development only, it's not a release target platform)

Test scenario

• Registration: The nodes can be registered by FND
• Metrics: Nodes send metrics successfully
• EFR32 Wi-SUN node can be pinged from FND
• EFR32 Wi-SUN node't metrics can be updated from FND

[ismilak]

@ismilak: I’ve reviewed some portion of the overall changes in this PR#22.

Changes look good under and the build/makefile udpates

osal/efr32_wisun
osal/freertos
osal/linux

Changes under /src are in review.

Changes under /sample, we see a lot of refactorization of the sample application code into multiple files. Per our last discussion we agreed to move only the TLV GET/PUT implementations to a separate file(now moved under tlvs/_tlvs.c), while keeping the rest in the original sample/CsmpAgentLib_sample.[ch]

sample_tlvs.[ch]
sample_util.[ch]
tlvs/efr32_wisun_tlvs.c
tlvs/freertos_tlvs.c
tlvs/linux_tlvs.c

Yep, let me explain the purposes of the source files.

• _sample/CsmpAgentLib_sampletlvs.h: It includes the common function declarations, like osal.h. These function implementations are platform specifics. They are implemented in _sample/tlvs/xxxxxtlvs.c files. It includes the function declaration of _csmptlvsget() and _csmptlvspost() handlers too.

• _sample/CsmpAgentLib_sampletlvs.c: This source includes only 2 function implementation: _csmptlvsget() and _csmptlvspost(). These functions are the common handlers, they are registered as callbacks in the handler instance.

• _sample/CsmpAgentLib_sampleutil.[ch]: These sources should include the utility functions, they can be used in the entire namespace of the sample application (sample/ dir). I note that, there is only one function yet (str2addr()) that is used only in _sample/CsmpAgentLibsample.c

The files are created to separate APIs and function implementations based on their functionality. I think what we can change to reduce the count of the files in sample/ directory:

• Moving _sample/CsmpAgentLib_sampletlvs.c content back to _sample/CsmpAgentLibsample.c and moving the related declarations from _sample/CsmpAgentLib_sampletlvs.h into that file.
• Moving _sample/CsmpAgentLib_sampleutil.[ch] into _sample/CsmpAgentLibsample.c

I recommend to keep as it is to have this kind of architecture for future improvements and to reduce the length of sample source files.