WIP: add support for preview 2 components that target the wasi:cli world

[karthik2804]

This adds a field to the trigger similar to the http-trigger that needs to be set if running preview1 components.

[[trigger.command]]
component = "sample"
# executor = { type = "preview1" }

This PR adds the ability for the trigger to support preview 2 components along with modules as well. It does it by attempting to load things as a component but falling back to attempting to load modules. The one other constraint it includes is that any preview 2 component supplied must target the wasi:cli world.

[radu-matei]

Can we infer preview1 vs. preview2 without having to explicitly set it in the manifest?

[karthik2804]

We can attempt to load as a component and fall back to a module. I just tested it locally, and it appears to work as expected.

[fibonacci1729]

nit: leave a TODO to pin to the Spin 2.4 release for these dependencies.

[radu-matei]

Do we need to pin to 2.4?

I pinned to 2.3.1 earlier so this can be imported in the containerd shim.

[fibonacci1729]

That's a good point and probably necessitates implementing this in terms of what's available in 2.3.1.

I only noticed the upgrade to the various new traits used below that will be made available in 2.4

[karthik2804]

These can definitely be implemented pinned to 2.3.1 but I upgraded as I was following the example of the http-trigger. Do we think pinning it to 2.3.1 is a necessity or will the shim be updated to 2.4.0 once that is released?

[radu-matei]

We'll bump everything once 2.4 is out.

[radu-matei]

Tested this with both Preview 1 and Preview 2 components and everything looks good. Merging so we can iterate. Thanks!