winch: Adding support for integration tests (#5588)

* Adding in the foundations for Winch `filetests`

This commit adds two new crates into the Winch workspace:
`filetests` and `test-macros`. The intent is to mimic the
structure of Cranelift `filetests`, but in a simpler way.

* Updates to documentation

This commits adds a high level document to outline how to test Winch
through the `winch-tools` utility. It also updates some inline
documentation which gets propagated to the CLI.

* Updating test-macro to use a glob instead of only a flat directory

Cargo.lock

@@ -766,9 +766,12 @@ dependencies = [
  "log",
  "pretty_env_logger",
  "rayon",
+ "serde",
+ "similar",
  "target-lexicon",
  "termcolor",
  "thiserror",
+ "toml",
  "walkdir",
  "wat",
 ]
@@ -3949,6 +3952,33 @@ dependencies = [
  "wasmparser",
 ]
 
+[[package]]
+name = "winch-filetests"
+version = "0.0.0"
+dependencies = [
+ "anyhow",
+ "capstone",
+ "cranelift-codegen",
+ "serde",
+ "similar",
+ "target-lexicon",
+ "toml",
+ "wasmtime-environ",
+ "wat",
+ "winch-codegen",
+ "winch-test-macros",
+]
+
+[[package]]
+name = "winch-test-macros"
+version = "0.0.0"
+dependencies = [
+ "glob",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "winch-tools"
 version = "0.0.0"
@@ -3957,11 +3987,17 @@ dependencies = [
  "capstone",
  "clap 3.2.8",
  "cranelift-codegen",
+ "glob",
+ "serde",
+ "similar",
  "target-lexicon",
+ "toml",
  "wasmparser",
  "wasmtime-environ",
  "wat",
  "winch-codegen",
+ "winch-filetests",
+ "winch-test-macros",
 ]
 
 [[package]]