Dev/wasmtime

[leon-thomm]

This PR adds a Wasmtime backend using Wasmtime for function isolation. The backend has two flavors:

• One which directly runs Wasm binaries on the Wasmtime VM, activated with feature flag dandelion-wasmtime-jit
• One using Wasmtime pre-compilation, activated with feature flag dandelion-wasmtime-precomp

[tom-kuchler]

Also should add the new features to the workflow so they will be tested on updates (need to resolve the merge conflicts for the workflow to run as I understand)

[leon-thomm]

• added wasmtime-precomp feature to dispatcher
• removed prints from build.rs
• cfg gated Elf config
• moved context loading into Wasmime engine file
• removed old WasmtimeContext
• added Wasm size check to WasmtimeContext, and made it always round up to next page
  • one might want to do something similar for the Wasm backend

[leon-thomm]

The dispatcher domain tests need a rework soon. For the Wasmtime backend, some of them fail because we now round up the context size (and they check whether reading or writing contexts OOB fails). Others fail because they try to use freestanding contexts, which will panic in the WasmtimeContext (must be loaded with a function config first).