chore(tvix/[ca]store): allow building without tonic-reflection

- rename the feature to `tonic-reflection` in both tvix-store and tvix-
   castore.
 - set it to disabled in tvix-castore by default
 - enable it in tvix-store, and pull in tvix-castore with the feature
   enabled.

Change-Id: Ie22833d85569502cae55812f6eeb17a9c15b9e2c
Reviewed-on: https://cl.tvl.fyi/c/depot/+/9472
Autosubmit: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI
Reviewed-by: raitobezarius <tvl@lahfa.xyz>

tvix/castore/src/proto/mod.rs

@@ -16,7 +16,7 @@ use crate::B3Digest;
 
 tonic::include_proto!("tvix.castore.v1");
 
-#[cfg(feature = "reflection")]
+#[cfg(feature = "tonic-reflection")]
 /// Compiled file descriptors for implementing [gRPC
 /// reflection](https://github.com/grpc/grpc/blob/master/doc/server-reflection.md) with e.g.
 /// [`tonic_reflection`](https://docs.rs/tonic-reflection).