Implement the bindle source for a local application

[radu-matei]

The component source configuration can be a reference and parcel pointing to a remote bindle. This should be implemented in the loader:

https://github.com/fermyon/spin/blob/75668c3569701050b7266a408d235d0c4eed318f/crates/loader/src/local/mod.rs#L109-L111

[lann]

Fixed by #456