Enable pushing components with spin registry push

[mikkelhegn]

#1182 and #2524 are part of enabling pushing and pulling components to/from registries.

With #2524 in Spin 2.6.0, there is a gap in how a sinlge component, can be pushed to a registry. If e.g., you create a WASI-HTTP incoming-handler, and want to push it to a registry, you hvae to use a tool like Oras.

The workflow works, using spin registry push today, but you can only do that if a spin.toml file is present in the diretory from which you push the component.

I'd like to prospoe adding an option to push a component using spin registry push - e.g., spin registry push component ttl.sh/my/name:0.0.1 -f my_component.wasm, to make this workflow easier.

[lann]

There will soon be another option here: wkg oci push

[itowlson]

@mikkelhegn Should we combine this with #2536? They seem to be asking for very similar things.

[mikkelhegn]

@itowlson - Thy seem undoubtfully similar :-) Let me close this one, and we can rack the other.

Closing as a duplicate of #2536