chore(tvix): add missing clippy attributes & config

For cases where clippy lints don't apply to us, or something is
misfiring, add appropriate configuration.

Relates to b/321.

Change-Id: I0af453910b4a4112bf685b2a8e9a73de10ec87ea
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9965
Reviewed-by: flokli <flokli@flokli.de>
Autosubmit: tazjin <tazjin@tvl.su>
Tested-by: BuildkiteCI

tvix/store/src/fs/mod.rs

@@ -93,6 +93,7 @@ pub struct TvixStoreFs {
     inode_tracker: RwLock<InodeTracker>,
 
     /// This holds all open file handles
+    #[allow(clippy::type_complexity)]
     file_handles: RwLock<HashMap<u64, Arc<tokio::sync::Mutex<Box<dyn BlobReader>>>>>,
 
     next_file_handle: AtomicU64,