feat(file_system): Add APIs for getting file paths and refactor implementation

Description

Update espp::FileSystem to support new APIs for setting read_only and grow_on_mount before mounting
Update espp::FileSystem to move string serialization of permissions and file times to separate reusable functions
Add espp::FileSystem::get_files_in_path(path, include_directories, recursive) method to allow callers to operate on files / directories more effectively than having to do string parsing
Refactored to move bulk of implementation of FileSystem into cpp

Gives users more control over how the file system is mounted
Simplifies compilation and reduces size of main binary by putting code into separate translation unit
Adds APIs so users can operate of files / directories more effectively

Building and running file_system/example on a QtPy ESP32S3.

CleanShot 2024-06-28 at 09 08 19

[ ] Bug fix (non-breaking change which fixes an issue)
[x] New feature (non-breaking change which adds functionality)
[ ] 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

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

[x] 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.