Shuffle around the wiggle crates (#1414)

* Shuffle around the wiggle crates

This commit reorganizes the wiggle crates slightly by performing the
following transforms:

* The `crates/wiggle` crate, previously named `wiggle`, was moved to
  `crates/wiggle/crates/macro` and is renamed to `wiggle-macro`.

* The `crates/wiggle/crates/runtime` crate, previously named
  `wiggle-runtime`, was moved to `crates/wiggle` and is renamed to
  `wiggle`.

* The new `wiggle` crate depends on `wiggle-macro` and reexports the macro.

The goal here is that consumers only deal with the `wiggle` crate
itself. No more crates depend on `wiggle-runtime` and all dependencies
are entirely on just the `wiggle` crate.

* Remove the `crates/wiggle/crates` directory

Move everything into `crates/wiggle` directly, like `wasi-common`

* Add wiggle-macro to test-all script

* Fixup a test

crates/wasi-common/src/path.rs

@@ -4,7 +4,7 @@ use crate::wasi::{types, Errno, Result};
 use crate::{entry::Descriptor, entry::Entry};
 use std::path::{Component, Path};
 use std::str;
-use wiggle_runtime::{GuestBorrows, GuestPtr};
+use wiggle::{GuestBorrows, GuestPtr};
 
 pub(crate) use sys::path::*;