Add Filesize type (#14369)

# Description
Adds a new `Filesize` type so that `FromValue` can be used to convert a
`Value::Filesize` to a `Filesize`. Currently, to extract a filesize from
a `Value` using `FromValue`, you have to extract an `i64` which coerces
`Value::Int`, `Value::Duration`, and `Value::Filesize` to an `i64`.

Having a separate type also allows us to enforce checked math to catch
overflows. Similarly, it allows us to specify other trait
implementations like `Display` in a common place.

# User-Facing Changes
Multiplication with filesizes now error on overflow. Should not be a
breaking change for plugins (i.e., serialization) since `Filesize` is
marked with `serde(transparent)`.

# Tests + Formatting
Updated some tests.

crates/nuon/src/lib.rs

@@ -155,7 +155,7 @@ mod tests {
     #[test]
     fn filesize() {
         nuon_end_to_end("1024b", Some(Value::test_filesize(1024)));
-        assert_eq!(from_nuon("1kib", None).unwrap(), Value::test_filesize(1024),);
+        assert_eq!(from_nuon("1kib", None).unwrap(), Value::test_filesize(1024));
     }
 
     #[test]