Add missing call to close sockets on nanoHAL_Uninitialize

[josesimoes]

Description

• Add missing call to close sockets on nanoHAL_Uninitialize.
• Add stub for SOCKETS_CloseConnections.

Motivation and Context

• Without this any open socket would remain opened after CLR shutdown causing issues on the next execution. This is because the lwIP threads and network interface persist even after nanoHAL_Uninitialize.
• STM32 ChibiOS still need a way to gracefully shutdown lwIP.

How Has This Been Tested?

Screenshots

Types of changes

• Improvement (non-breaking change that improves a feature, code or algorithm)
• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

Signed-off-by: José Simões jose.simoes@eclo.solutions

[nfbot]

Hi @josesimoes,

I'm nanoFramework bot.
Thank you for your contribution!

A human will be reviewing it shortly. 😉