chore(release): 0.3.1 with workspace split (#186)

## Motivation

Releasing 0.3.0 required a working-tree hack: the test harness depends
on `trussed-staging`, which isn't on crates.io and won't be published,
so its presence in the dev-deps blocked `cargo publish`. Each release
otherwise needs a manual dance to comment things out and revert.
Splitting the trussed-coupled test code into a non-published sibling
crate makes `cargo publish` clean and removes the recurring chore.

## Summary

Splits the repo into a Cargo workspace with two members:

- `libwebauthn` (publishable). Adds an opt-in `virt` feature that
exposes a small `HidPipeBackend` trait and a `virtual_device(backend)`
constructor. No trussed coupling in the published crate.
- `libwebauthn-tests` (`publish = false`). Owns the
trussed-staging-backed `TrussedVirtBackend` impl plus all integration
tests.

`cargo publish -p libwebauthn` now works without any working-tree hacks.
The workspace `[patch.crates-io]` keeps the trussed git pins for tests.

## Notable changes

- `cfg(test)` gates that integrated virt into production types in
`transport/hid/{device,channel}.rs`, `transport/{mod,channel}.rs` are
now `cfg(feature = "virt")`. Same for the `pin_protocol_override` hook
and the test-only `PartialEq` impls in `lib.rs`.
- `ctap2_preflight` is now `pub` so the preflight tests can run as
integration tests in libwebauthn-tests.
- The panic/unwrap deny lints in `lib.rs` are gated by `not(any(test,
feature = "virt"))` so the virt code path may use them.
- CI runs against the workspace (`cargo build --workspace`, `cargo test
--workspace`, etc.) and now also runs `cargo publish --dry-run -p
libwebauthn` as a check.

## Test plan

- [x] `cargo build -p libwebauthn` (no virt feature)
- [x] `cargo build -p libwebauthn --features virt`
- [x] `cargo build --workspace --all-targets --all-features`
- [x] `cargo fmt --all -- --check`
- [x] `cargo clippy --workspace --all-targets --all-features -- -D
warnings`
- [x] `cargo test --workspace` (134 tests pass)
- [x] `cargo publish --dry-run -p libwebauthn` (clean, no hacks)

Author: AlfioEmanueleFresta

.github/workflows/rust-clippy.yml

@@ -44,6 +44,7 @@ jobs:
       - name: Run rust-clippy
         run:
           cargo clippy
+          --workspace
           --all-features
           --message-format=json | clippy-sarif | tee rust-clippy-results.sarif | sarif-fmt
         continue-on-error: true

.github/workflows/rust.yml

@@ -7,10 +7,6 @@ jobs:
       RUST_LOG: debug
     name: Build and run tests
     runs-on: ubuntu-latest
-    # Set the default working directory for all 'run' steps in this job
-    defaults:
-      run:
-        working-directory: libwebauthn/
     steps:
       - uses: actions/checkout@v2
       - name: Checkout submodules
@@ -20,10 +16,12 @@ jobs:
       - name: Install system dependencies
         run: sudo apt-get install libudev-dev libdbus-1-dev libsodium-dev libnfc-dev libpcsclite-dev
       - name: Clippy
-        run: cargo clippy --all-targets --all-features -- -D warnings
+        run: cargo clippy --workspace --all-targets --all-features -- -D warnings
       - name: Check formatting
-        run: cargo fmt -- --check
+        run: cargo fmt --all -- --check
       - name: Build
-        run: cargo build --all-targets --all-features
+        run: cargo build --workspace --all-targets --all-features
       - name: Run tests
-        run: cargo test --verbose
+        run: cargo test --workspace --verbose
+      - name: Verify libwebauthn publishes cleanly
+        run: cargo publish --dry-run -p libwebauthn