Implement new error handling pattern for scripting

[coal-rock]

New Error Type

Errors now can be described through the following syntax from within Rust:

pub enum ScriptError {
    #[strum(props(class = "fs", name = "OtherFs"), to_string = "{0}")]
    FsError(String),

    #[strum(
        props(class = "fs", name = "FileNotFound"),
        to_string = "could not find file at path: \"{file_path}\""
    )]
    FsFileNotFound { file_path: String },
    ....
  }

Additionally, fs has been migrated to specifically use these errors, and existing errors should continue to function in a second-class manor until manual work is done to port them over.

Use from Rhai

The following getters were created to better take advantage of new context-rich errors:

.class

Returns the class that this error belongs to:

try {
  fs::remove("/"); // rm -rf :P
  sys::reboot();   // it's so joever for them!!!
}
catch (error) {
  switch(error.class) {
    "sys" => print("there was some error relating to the sys module"),
    "fs" => print("there was some error relating to the fs module"),
    _ => print("some other error occurred"),
  }
}

.name

Returns a deterministic string that can be matched upon to identify error type:

try {
   let seed = fs::read("/home/coal/Important/MoneroSeed");
   print("all your monero is mine!!");
   print(seed);
}
catch (error) {
   switch(error.name) {
       "FileNotFound" => print("the monero seed does not exist"),
       "PermissionDenied" => print("no permission to read the monero seed"),
       "IsADirectory" => print("monero seed path is a directory"),
       "InvalidUTF8" => print("monero seed does not contain valid UTF-8"),
       "OtherFs" => print("some other filesystem error occurred:" + error.msg),
       _ => print("some other error occurred"),
   }
}

.msg

Returns message containing human readable description of the error:

try {
   let homework = fs::read("/home/ruby/homework/calc1.mp4");
}
catch (error) {
   print(error.msg); // `file: "/home/ruby/homework/calc1.mp4" contains invalid utf-8`
}

.pretty

Returns a pretty print of the error:

try {
   let homework = fs::read("/home/ruby/homework/calc1.mp4");
}
catch (error) {
   print(error.pretty); // `[fs] InvalidUTF8 - file: "/home/ruby/homework/calc1.mp4" contains invalid utf-8`
}

[engelhartrueben]

LGTM 🚀