Work on power down sequence

[josesimoes]

Description

• Moved PowerLevel enum to nanoHAL_Power. Rework code accordingly.
• Add check for reboot request and power mode after execution engine exits.
• Add new function (to implemente at target level) to handle setting CPU power mode.
• Update Win32 nanoCLR project accodingly.

Motivation and Context

• The current "go-to-sleep" implementation is too simplistic because it does not have a way to gracefully exiting the execution engine (threads execution isn't terminated, disposed isn't called). Besides that it requires (at least formally) that the underlying OS is properly executing a recommended shut-down sequence.
• The new approach requires that the "go-to-sleep" C# call just flags the reboot and power mode to the requested level, the execution engine gracefuller exits and after that each target has the opportunity to handle the shut-down sequence on it's own way.

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. 😉

[josesimoes]

@nanoframework/esp32-developers any comments on this?

The next step to make this happen is adjusting the code in nanoFramework_Hardware_Esp32_Sleep::NativeStartDeepSleep.