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/store/build.rs

@@ -4,7 +4,7 @@ fn main() -> Result<()> {
     #[allow(unused_mut)]
     let mut builder = tonic_build::configure();
 
-    #[cfg(feature = "reflection")]
+    #[cfg(feature = "tonic-reflection")]
     {
         let out_dir = std::path::PathBuf::from(std::env::var("OUT_DIR").unwrap());
         let descriptor_path = out_dir.join("tvix.store.v1.bin");