chore(*): bump spin and co. crates to v3.0.0

[vdice]

• Bump spin crates to https://github.com/fermyon/spin/releases/tag/v3.0.0
  • Also update usage in src/lib.rs (thanks @fibonacci1729!)
• Bump wasmtime to match Spin
• De-bump tokio from 1.40 to 1.38*

Tested via the example apps.

*This was done to address the following compilation conflict:

$ cargo build --release
    Updating crates.io index
    Updating git repository `https://github.com/fermyon/spin`
error: failed to select a version for `tokio`.
    ... required by package `trigger-command v0.1.0 (/Users/vdice/code/github.com/fermyon/spin-trigger-command)`
versions that meet the requirements `^1.40` are: 1.40.0, 1.41.1, 1.41.0

all possible versions conflict with previously selected packages.

  previously selected package `tokio v1.38.0`
    ... which satisfies dependency `tokio = "~1.38.0"` of package `opentelemetry-otlp v0.25.0`
    ... which satisfies dependency `opentelemetry-otlp = "^0.25"` of package `spin-telemetry v3.0.0 (https://github.com/fermyon/spin?tag=v3.0.0#737778e9)`
    ... which satisfies git dependency `spin-telemetry` of package `trigger-command v0.1.0 (/Users/vdice/code/github.com/fermyon/spin-trigger-command)`

failed to select a version for `tokio` which could resolve this conflict

[radu-matei]

3.0!