Add support for the experimental wasi-crypto APIs (#2597)

* Add support for the experimental wasi-crypto APIs

The sole purpose of the implementation is to allow bindings and
application developers to test the proposed APIs.

Rust and AssemblyScript bindings are also available as examples.

Like `wasi-nn`, it is currently disabled by default, and requires
the `wasi-crypto` feature flag to be compiled in.

* Rename the wasi-crypto/spec submodule

* Add a path dependency into the submodule for wasi-crypto

* Tell the publish script to vendor wasi-crypto

crates/wasi-crypto/src/lib.rs

@@ -0,0 +1,31 @@
+mod wiggle_interfaces;
+
+pub use wiggle_interfaces::WasiCryptoCtx;
+
+wasmtime_wiggle::wasmtime_integration!({
+    target: wiggle_interfaces::wasi_modules,
+    witx: ["$CARGO_MANIFEST_DIR/spec/witx/wasi_ephemeral_crypto.witx"],
+    ctx: WasiCryptoCtx,
+    modules: {
+        wasi_ephemeral_crypto_common =>
+            {
+                name: WasiCryptoCommon,
+                docs: "wasi-crypto - Common module."
+            },
+        wasi_ephemeral_crypto_asymmetric_common =>
+            {
+                name: WasiCryptoAsymmetricCommon,
+                docs: "wasi-crypto - Common module for asymmetric operations."
+            },
+        wasi_ephemeral_crypto_signatures =>
+            {
+                name: WasiCryptoSignatures,
+                docs: "wasi-crypto - Signature module."
+            },
+        wasi_ephemeral_crypto_symmetric =>
+            {
+                name: WasiCryptoSymmetric,
+                docs: "wasi-crypto - Symmetric cryptography module."
+            }
+    }
+});