async-await: add current_thread::Runtime::block_on_async (#1072)

This function is used by the Tokio macros introduced by #1058  but was
omitted from the PR.

ci/azure-cargo-check.yml

@@ -27,7 +27,3 @@ jobs:
       - script: cargo check ${{ parameters.noDefaultFeatures }} --features ${{ feature }}
         displayName: Check `${{ crate.key }}`, features = ${{ feature }}
         workingDirectory: $(Build.SourcesDirectory)/${{ crate.key }}
-
-  - ${{ if parameters.benches }}:
-    - script: cargo check --benches --all
-      displayName: Check benchmarks