feat(nvs): refactor espp::Nvs to use espp::NvsHandle

[finger563]

Description

• Move error codes out of nvs/nvs_handle headers and into nvs_errc.hpp
• Rename espp::NVSHandle -> espp::NvsHandle
• Add espp::NvsHandle::get(key, value, default, error_code) which allows a get_or_set paradigm to configure default if no value is present
• Refactor espp::Nvs to use espp::NvsHandle which greatly simplifies espp::Nvs and allows for maximum code reuse.

Motivation and Context

After #257 we had duplicated code for managing nvs stored data. That PR provided a nice espp::NvsHandle implementation, which could be used to replace and simplify the implementation of espp::Nvs.

This PR performs that refactor, and updates the espp::NvsHandle to have all the necessary overloads to do so.

How has this been tested?

Building and running the nvs/example on a QtPy ESP32S3 and rebooting it through enough cycles to erase the flash.

Screenshots (if appropriate, e.g. schematic, board, console logs, lab pictures):

When erasing the flash:

After erasing the flash:

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to not work as expected)
• [ ] Documentation Update
• [ ] Hardware (schematic, board, system design) change
• [x] Software change

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have added / updated the documentation related to this change via either README or WIKI

Software

• [ ] I have added tests to cover my changes.
• [ ] I have updated the .github/workflows/build.yml file to add my new test to the automated cloud build github action.
• [x] All new and existing tests passed.
• [x] My code follows the code style of this project.

[github-actions[bot]]

:white_check_mark:Static analysis result - no issues found! :white_check_mark: