Add newly merged stories

As agreed to merge during meeting 2021-06-25 add these stories. Alphabetic arrangement

Alan misses C# async
Barbara begets backpressure and benchmarks async_trait
Barbara polls a Mutex
Barbara wants single threaded optimizations

Author: doc-jones

src/SUMMARY.md

@@ -23,19 +23,20 @@
       - [SLOW (Protocol implementation)](./vision/projects/SLOW.md)
    - [😱 Status quo](./vision/status_quo.md)
       - [Template](./vision/status_quo/template.md)
-      - [Alan tries to cache requests, which doesn't always happen](./vision/status_quo/alan_builds_a_cache.md)
       - [Alan finds dropping database handles is hard](./vision/status_quo/alan_finds_database_drops_hard.md)
       - [Alan has an external event loop](./vision/status_quo/alan_has_an_event_loop.md)
       - [Alan hates writing a `Stream`](./vision/status_quo/alan_hates_writing_a_stream.md)
       - [Alan iteratively regresses performance](./vision/status_quo/alan_iteratively_regresses.md)
       - [Alan lost the world](./vision/status_quo/alan_lost_the_world.md)
+      - [Alan misses C# async](./vision/status_quo/alan_misses_c_sharp_async.md)
       - [Alan needs async in traits](./vision/status_quo/alan_needs_async_in_traits.md)
-      - [Alan wants to migrate a web server to Rust](./vision/status_quo/alan_picks_web_server.md)
       - [Alan runs into stack trouble](./vision/status_quo/alan_runs_into_stack_trouble.md)
       - [Alan started trusting the Rust compiler, but then... async](./vision/status_quo/alan_started_trusting_the_rust_compiler_but_then_async.md)
       - [Alan thinks he needs async locks](./vision/status_quo/alan_thinks_he_needs_async_locks.md)
       - [Alan tries using a socket Sink](./vision/status_quo/alan_tries_a_socket_sink.md)
       - [Alan tries to debug a hang](./vision/status_quo/alan_tries_to_debug_a_hang.md)
+      - [Alan tries to cache requests, which doesn't always happen](./vision/status_quo/alan_builds_a_cache.md)
+      - [Alan wants to migrate a web server to Rust](./vision/status_quo/alan_picks_web_server.md)
       - [Alan writes a web framework](./vision/status_quo/alan_writes_a_web_framework.md)
       - [Alan extends an AWS service](./vision/status_quo/aws_engineer.md)
          - [Writing a Java-based service at AWS](./vision/status_quo/aws_engineer/writing_a_java_based_service.md)
@@ -53,7 +54,9 @@
          - [Debugging performance problems](./vision/status_quo/aws_engineer/debugging_performance_problems.md)
          - [Using JNI](./vision/status_quo/aws_engineer/using_jni.md)
       - [Barbara anguishes over HTTP](./vision/status_quo/barbara_anguishes_over_http.md)
+      - [Barbara awants single threaded optimizations](./vision/status_quo/barbara_wants_single_threaded_optimizations.md)
       - [Barbara battles buffered streams](./vision/status_quo/barbara_battles_buffered_streams.md)
+      - [Barbara begets backpressure and benchmarks async_trait](./vision/status_quo/barbara_benchmarks_async_trait.md)
       - [Barbara bridges sync and async in `perf.rust-lang.org`](./vision/status_quo/barbara_bridges_sync_and_async.md)
       - [Barbara builds an async executor](./vision/status_quo/barbara_builds_an_async_executor.md)
       - [Barbara carefully dismisses embedded `Future`](./vision/status_quo/barbara_carefully_dismisses_embedded_future.md)
@@ -62,6 +65,7 @@
       - [Barbara makes their first foray into async](./vision/status_quo/barbara_makes_their_first_steps_into_async.md)
       - [Barbara needs Async Helpers](./vision/status_quo/barbara_needs_async_helpers.md)
       - [Barbara plays with async](./vision/status_quo/barbara_plays_with_async.md)
+      - [Barbara polls a Mutex](./vision/status_quo/barbara_polls_a_mutex.md)
       - [Barbara tries async streams](./vision/status_quo/barbara_tries_async_streams.md)
       - [Barbara tries Unix socket](./vision/status_quo/barbara_tries_unix_socket.md)
       - [Barbara trims a stacktrace](./vision/status_quo/barbara_trims_a_stacktrace.md)