peepmatic: Be generic over the operator type

This lets us avoid the cost of `cranelift_codegen::ir::Opcode` to
`peepmatic_runtime::Operator` conversion overhead, and paves the way for
allowing Peepmatic to support non-clif optimizations (e.g. vcode optimizations).

Rather than defining our own `peepmatic::Operator` type like we used to, now the
whole `peepmatic` crate is effectively generic over a `TOperator` type
parameter. For the Cranelift integration, we use `cranelift_codegen::ir::Opcode`
as the concrete type for our `TOperator` type parameter. For testing, we also
define a `TestOperator` type, so that we can test Peepmatic code without
building all of Cranelift, and we can keep them somewhat isolated from each
other.

The methods that `peepmatic::Operator` had are now translated into trait bounds
on the `TOperator` type. These traits need to be shared between all of
`peepmatic`, `peepmatic-runtime`, and `cranelift-codegen`'s Peepmatic
integration. Therefore, these new traits live in a new crate:
`peepmatic-traits`. This crate acts as a header file of sorts for shared
trait/type/macro definitions.

Additionally, the `peepmatic-runtime` crate no longer depends on the
`peepmatic-macro` procedural macro crate, which should lead to faster build
times for Cranelift when it is using pre-built peephole optimizers.

.github/workflows/main.yml

@@ -163,10 +163,16 @@ jobs:
           --package peepmatic-runtime \
           --package peepmatic-test
     - name: Rebuild Peepmatic-based peephole optimizers and test them
-      run: cargo test --features 'enable-peepmatic cranelift-codegen/rebuild-peephole-optimizers'
+      run: |
+        cargo test \
+          --features 'enable-peepmatic cranelift-codegen/rebuild-peephole-optimizers' \
+          peepmatic
       working-directory: ./cranelift
-    - name: Check that peephole optimizers are up to date
+    - name: Check that built peephole optimizers are up to date
       run: git diff --exit-code
+    - name: Test with Peepmatic-based peephole optimizers
+      run: cargo test --features 'enable-peepmatic'
+      working-directory: ./cranelift
 
   # Perform all tests (debug mode) for `wasmtime`. This runs stable/beta/nightly
   # channels of Rust as well as macOS/Linux/Windows.