Primitive Types

Primitive types map (mostly) idiomatically:

AIDL Type	Rust 型	Note
`boolean`	`bool`
`byte`	`i8`	Note that bytes are signed.
`char`	`u16`	Note the usage of `u16`, NOT `u32`.
`int`	`i32`
`long`	`i64`
`float`	`f32`
`double`	`f64`
`String`	`String`