Get rid of old non-factors code

[rylev]

This deletes the following:

• trigger, trigger-http, and trigger-redis`
• All the old "host-component" crates
• spin-testing that was only be used in one place, the spin-oci crate (we'll need to find a replacement for that test)
• builds of several test apps that I believe are no longer used anywhere

Some notes:

• We haven't yet ported trigger-redis over to factors, but I think it's fine if we delete the existing crate (we have git history)
• We needed to comment out a dependency of the timer trigger example, but that didn't build anyway. We'll need to port it to factors.
• We'll want to rename crates (e.g., trigger2 -> trigger), but I'll do that in a follow up.