update WASI submodule (#3025)

* wasi-common: update wasi submodule

This updates the WASI submodule, pulling in changes to the witx crate,
now that there is a 0.9.1 version including some bug fixes. See
WebAssembly/WASI#434 for more information.

* wiggle: update witx dependencies

* publish: verify and vendor witx-cli

* adjust root workspace members

This commit removes some items from the root manifest's workspace
members array, and adds `witx-cli` to the root `workspace.exclude`
array.

The motivation for this stems from a cargo bug described in
rust-lang/cargo#6745: `workspace.exclude` does not work if it is nested
under a `workspace.members` path.

See WebAssembly/WASI#438 for the underlying change to the WASI submodule
which reorganized the `witx-cli` crate, and WebAssembly/WASI#398 for the
original PR introducing `witx-cli`.

See [this
comment](https://github.com/bytecodealliance/wasmtime/pull/3025#issuecomment-867741175)
for more details about the compilation errors, and failed alternative
approaches that necessitated this change.

N.B. This is not a functional change, these crates are still implicitly
workspace members as transitive dependencies, but this will allow us to
side-step the aforementioned cargo bug.

Co-Authored-By: Alex Crichton <alex@alexcrichton.com>

Co-authored-by: Alex Crichton <alex@alexcrichton.com>

crates/wiggle/macro/Cargo.toml

@@ -22,7 +22,7 @@ doctest = false
 
 [dependencies]
 wiggle-generate = { path = "../generate", version = "0.28.0" }
-witx = { version = "0.9.0", path = "../../wasi-common/WASI/tools/witx" }
+witx = { version = "0.9.1", path = "../../wasi-common/WASI/tools/witx" }
 quote = "1.0"
 syn = { version = "1.0", features = ["full"] }
 proc-macro2 = "1.0"