Implement RFC 11: Redesigning Wasmtime's APIs (#2897)

Implement Wasmtime's new API as designed by RFC 11. This is quite a large commit which has had lots of discussion externally, so for more information it's best to read the RFC thread and the PR thread.

crates/wiggle/Cargo.toml

@@ -17,14 +17,33 @@ wiggle-macro = { path = "macro", version = "0.27.0" }
 tracing = "0.1.15"
 bitflags = "1.2"
 async-trait = "0.1.42"
+wasmtime = { path = "../wasmtime", version = "0.27.0", optional = true, default-features = false }
+anyhow = "1.0"
 
 [badges]
 maintenance = { status = "actively-developed" }
 
 [dev-dependencies]
 wiggle-test = { path = "test-helpers" }
+anyhow = "1"
 proptest = "1.0.0"
 
+[[test]]
+name = "wasmtime_async"
+path = "tests/wasmtime_async.rs"
+required-features = ["wasmtime_async", "wasmtime/wat"]
+
+[[test]]
+name = "wasmtime_sync"
+path = "tests/wasmtime_sync.rs"
+required-features = ["wasmtime_integration", "wasmtime/wat"]
+
+[[test]]
+name = "wasmtime_integration"
+path = "tests/wasmtime_integration.rs"
+required-features = ["wasmtime_integration", "wasmtime/wat"]
+
+
 [features]
 # The wiggle proc-macro emits some code (inside `pub mod metadata`) guarded
 # by the `wiggle_metadata` feature flag. We use this feature flag so that
@@ -38,4 +57,9 @@ wiggle_metadata = ['witx', "wiggle-macro/wiggle_metadata"]
 # the logs out of wiggle-generated libraries.
 tracing_log = [ "tracing/log" ]
 
-default = ["wiggle_metadata" ]
+# Generate adapters for wasmtime, and expose the wasmtime_integration macro.
+wasmtime_integration = [ "wasmtime", "wiggle-macro/wasmtime" ]
+# Support for async in the wasmtime crates.
+wasmtime_async = [ "wasmtime_integration", "wasmtime/async" ]
+
+default = ["wiggle_metadata", "wasmtime_integration" ]