refactor: use async-aware RwLocks and Mutexes where possible

squashed from https://gitlab.com/famedly/conduit/-/merge_requests/595

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/lib.rs

@@ -4,6 +4,10 @@ mod database;
 mod service;
 mod utils;
 
+// Not async due to services() being used in many closures, and async closures
+// are not stable as of writing This is the case for every other occurence of
+// sync Mutex/RwLock, except for database related ones, where the current
+// maintainer (Timo) has asked to not modify those
 use std::sync::RwLock;
 
 pub use api::ruma_wrapper::{Ruma, RumaResponse};