`Vec1` is used by `RecordType` to ensure that a record have at least 1
field. Then an `InterfaceValue::Record` is ensured to get at least one
value with the type-checking pass.
The `Type::Record` variant now is defined by `RecordType`. In
addition, `InterfaceType` has a new variant: `Record`, that is also
defined by `RecordType`. Encoders and decoders are updated to consider
`RecordType`, which removes code duplication and simplify code.
This patch updates the `Type` type to be an enum with 2 variants:
`Function` and `Record`, resp. to represent:
1. `(@interface type (func (param i32 i32) (result string)))`
2. `(@interface type (record string i32))`
This patch updates the binary encoder and decoder, along with the WAT
encoder and decoder.
Basically the `x-to-y` instructions have been renamed `y.from_x`. This
patch updates the instruction. The binary representation isn't
specified yet, so it's just arbitrary values.
According to the last working notes, new interface types are s8, s16,
s32, s64, u8, u16, u32, u64, f32, f64, string, anyref, i32, and i64.
Their binary reprensentations are changing too, from 0x00 to 0x0d.
