Fix potential memory leak in System.IO

[morali]

Description

New implementation of System.IO allocates memory and frees it only if fatfs methods return without error. This can lead to memory leak, if for example f_open method fails. I added CLEANUP() sections in native methods for freeing memory allocated on heap and closing file handles.

Motivation and Context

Fixes memory leak in System.IO

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.

[dnfadmin]

All CLA requirements met.

[nfbot]

@morali there are issues with the code style on the source files.
A PR was submitted with the code style fixes. Please review and merge the changes. See morali#1.

Make sure you are using the project code style. Check the details here.

[nfbot]

@morali there are issues with the code style on the source files.
A PR was submitted with the code style fixes. Please review and merge the changes. See morali#2.

Make sure you are using the project code style. Check the details here.

[nfbot]

@morali there are issues with the code style on the source files.
A PR was submitted with the code style fixes. Please review and merge the changes. See morali#3.

Make sure you are using the project code style. Check the details here.

[josesimoes]

Excellent! Thanks for taking care of this. 👏🏻 👍🏻