upgrade scale to v0.10.0

[tjjfvi]

Breaking changes were introduced in tjjfvi/subshape#128; most notably:

 const foo = $.object(
-  ["bar", $.u8],
-  ["baz", $.str],
+  $.field("bar", $.u8),
+  $.field("baz", $.str),
 )

For now, for simplicity, I think we should use $.field("foo", $.option($bar)) instead of $.optionalField("foo", $bar) in the codegen. But in the non-generated code, I see no reason not to use $.optionalField.