Add support for the `std_feature` flag in
`[package.metadata.component.bindings]`, so that cargo-component can
produce no_std components.

* Update dependencies to latest.

* Implement `unlocked-dep` imports for component dependencies.

This commit implements outputting a component with `unlocked-dep` imports for
any component dependencies specified in `Cargo.toml`.

Note that WIT does not support the nesting of interfaces (i.e.
instances), so to properly bind to a component's exports, an instance is
imported for its directly exported functions and then one for every instance
the component exports.

Therefore, depending on a component may result in more than one import
dependency for that package; one of the imports might be for
`unlocked-dep=<foo:bar>`, while others might be of the form
`unlocked-dep=<foo:bar/<export>>`.

* Update to Warg 0.3.0.

This includes a rename of `PackageId` to `PackageName` in various places.

* Fix incorrect import name map entry for interface exports.

The import name used in the bindings is the `id_of` the interface, and not just
the interface name.

* Bump Wasmtime version in CI.

* Bump version to 0.8.0.

This commit also bumps `wit` to 0.7.0.