sync: move CancellationToken tests (#2477)

In preparation of work on `CancellationToken` internals, the tests are
moved into `tests/` and are updated to not depend on internals.

ci/azure-check-features.yml

@@ -30,3 +30,9 @@ jobs:
   #   tracking-issue: https://github.com/rust-lang/cargo/issues/5133
   - script: cargo hack check --all --each-feature -Z avoid-dev-deps
     displayName: cargo hack check --all --each-feature
+
+  # Try with unstable feature flags
+  - script: cargo hack check --all --each-feature -Z avoid-dev-deps
+    displayName: cargo hack check --all --each-feature
+    env:
+      RUSTFLAGS: '--cfg tokio_unstable'

ci/azure-loom.yml

@@ -21,7 +21,7 @@ jobs:
     parameters:
       rust_version: ${{ parameters.rust }}
 
-  - script: RUSTFLAGS="--cfg loom" cargo test --lib --release --features "full" -- --nocapture $(scope)
+  - script: RUSTFLAGS="--cfg loom --cfg tokio_unstable" cargo test --lib --release --features "full" -- --nocapture $(scope)
     env:
       LOOM_MAX_PREEMPTIONS: 2
       CI: 'True'

ci/azure-test-stable.yml

@@ -21,6 +21,23 @@ jobs:
 
   - template: azure-is-release.yml
 
+  # Run `tokio` with only `full`
+  - script: cargo test --features full
+    env:
+      RUST_BACKTRACE: 1
+      CI: 'True'
+    displayName: tokio - cargo test --features full
+    workingDirectory: $(Build.SourcesDirectory)/tokio
+
+  # Run `tokio` with "unstable" cfg flag
+  - script: cargo test --all-features
+    env:
+      RUSTFLAGS: '--cfg tokio_unstable'
+      RUST_BACKTRACE: 1
+      CI: 'True'
+    displayName: tokio - cargo test --features full
+    workingDirectory: $(Build.SourcesDirectory)/tokio
+
   - ${{ each crate in parameters.crates }}:
     # Run with all crate features
     - script: cargo test --all-features