Remove restrictions:
- Only 1 WASM app at a time
- Only 1 model at a time
- `graph` and `graph-execution-context` are ignored
Refer to previous document:
e8d718096d/core/iwasm/libraries/wasi-nn/README.md
- Reorganize the library structure
- Use the latest version of `wasi-nn` wit (Oct 25, 2022):
0f77c48ec1/wasi-nn.wit.md
- Split logic that converts WASM structs to native structs in a separate file
- Simplify addition of new frameworks
