feat(tvix/tracing): gRPC trace context propagation

This introduces optional helper function in tvix/tracing for trace
propagation and uses these helper in the `tvix-store`.

The GRPCBlobService, GRPCDirectoryService and GRPCPathInfoService now
accept a generic client, meaning the client can be generated with either
`::new` or `::with_interceptor`.

This was tested and validated by starting a `tvix-store daemon` and
`tvix-store import`.

Change-Id: I4b194483bf09266820104b4b56e4a135dca2b77a
Reviewed-on: https://cl.tvl.fyi/c/depot/+/11863
Reviewed-by: flokli <flokli@flokli.de>
Tested-by: BuildkiteCI

tvix/tracing/Cargo.toml

@@ -17,6 +17,10 @@ opentelemetry = { version = "0.22.0", optional = true }
 opentelemetry-otlp = { version = "0.15.0", optional = true }
 opentelemetry_sdk = { version = "0.22.1", features = ["rt-tokio"], optional = true }
 tracing-tracy = { version = "0.11.0", features = ["flush-on-exit"], optional = true }
+opentelemetry-http = { version = "0.11.0", optional = true }
+
+tonic = { version = "0.11.0", optional = true }
+http  = { version = "0.2.11", optional = true }
 
 [features]
 default = []
@@ -24,11 +28,16 @@ otlp = [
   "dep:tracing-opentelemetry",
   "dep:opentelemetry",
   "dep:opentelemetry-otlp",
-  "dep:opentelemetry_sdk"
+  "dep:opentelemetry_sdk",
+  "dep:opentelemetry-http"
 ]
 tracy = [
   "dep:tracing-tracy"
 ]
+tonic = [
+  "dep:tonic",
+  "dep:http",
+]
 
 [lints]
 workspace = true