Fix EraseAsync

[josesimoes]

Description

• Improve code to erase all blocks (flash sectors).
• Remove useless code.
• Simplifications by using existing properties instead of pulling them again from the device.

Motivation and Context

• EraseAsync wasn't erasing all the flash sectors in the memory block only the 1st one.
• TODO possibly rename the FlashSectorData class and friends to match the names used in native code.

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)
• Config and build (change in the configuration and build system, has no impact on code or features)
• Dependencies (update dependencies and changes associated, has no impact on code or features)

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.