feat: initial file system operations

[Im-Beast]

Follow up to #3, most of the code has been reused.
This PR adds support for these API's (#6):

• fs
  • readFile – async read file and return Uint8Array
  • readFileSync – sync version of fs.readFile
  • readTextFile – async read file and return string
  • readTextFileSync – sync version of fs.readTextFile
  • writeFile – async write file using Uint8Array
  • writeFileSync – sync version of fs.writeFile
  • writeTextFile – async write file using string
  • writeTextFileSync – sync version of fs.readTextFile
  • removeFile - asynchronously delete file
  • removeFileSync - sync version of fs.removeFile
  • removeDirectory - asynchronously delete directory
  • removeDirectorySync - sync version of fs.removeDirectory

This PR doesn't use op2's, it can be done as a follow up
Most of the ops have been converted to op2, the only one that isn't is op_read_text_file