Add exception handlers for debug

[josesimoes]

Description

Add handlers for ARM exceptions that replace the default (and empty ones) from ChibiOS.

Motivation and Context

This aims to be a handy and helpful debugger tool.
Current handlers do not expose any details about the fault/exception that has occurred.
The debugger is not able to backtrack through exceptions because those are executed on a separate stack.
These handlers expose the NVIC registers and context in local vars allowing easy inspection of those.

How Has This Been Tested?

Causing a hard fault exception and verifying that the handler hits the break point there.

Types of changes

• 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. 😉