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/nu-command/src/conversions/into/binary.rs

@@ -147,7 +147,7 @@ pub fn action(input: &Value, _args: &Arguments, span: Span) -> Value {
         Value::Binary { .. } => input.clone(),
         Value::Int { val, .. } => Value::binary(val.to_ne_bytes().to_vec(), span),
         Value::Float { val, .. } => Value::binary(val.to_ne_bytes().to_vec(), span),
-        Value::Filesize { val, .. } => Value::binary(val.to_ne_bytes().to_vec(), span),
+        Value::Filesize { val, .. } => Value::binary(val.get().to_ne_bytes().to_vec(), span),
         Value::String { val, .. } => Value::binary(val.as_bytes().to_vec(), span),
         Value::Bool { val, .. } => Value::binary(i64::from(*val).to_ne_bytes().to_vec(), span),
         Value::Duration { val, .. } => Value::binary(val.to_ne_bytes().to_vec(), span),

crates/nu-command/src/conversions/into/int.rs

@@ -253,7 +253,7 @@ fn action(input: &Value, args: &Arguments, span: Span) -> Value {
                 convert_int(input, span, radix)
             }
         }
-        Value::Filesize { val, .. } => Value::int(*val, span),
+        Value::Filesize { val, .. } => Value::int(val.get(), span),
         Value::Float { val, .. } => Value::int(
             {
                 if radix == 10 {