schema: redesign v* package layout

[MrAlias]

Currently the schema module has the following package layout

schema
├── internal
├── v1.0
│   ├── ast
│   ├── testdata
│   └── types
└── v1.1
    ├── ast
    ├── testdata
    └── types

Using packages with v* has semantic meaning in Go.

Instead of using the v1.0 and v1.1 directory structure to partition the supported schema file versions, look into alternatives so if in the future there needs to be a v2 version of the `schema package we can accommodate this.