rust: add tonic-reflection dependency (#4871)

Summary:
The [`tonic-reflection`] crate implements the gRPC reflection protocol,
and will enable us to significantly simplify `grpc_cli` usage.

Reflection was released in Tonic v0.4.1, so this patch also upgrades the
rest of our Tonic stack to the latest versions.

[`tonic-reflection`]: https://crates.io/crates/tonic-reflection

Test Plan:
It builds: `bazel build //tensorboard/data/server/cargo:tonic_reflection`.

wchargin-branch: rust-dep-tonic-reflection

.github/workflows/ci.yml

@@ -146,6 +146,7 @@ jobs:
         with:
           toolchain: ${{ matrix.rust_version }}
           default: true
+          components: rustfmt
       - name: 'Install Python packaging deps'
         run: |
           python -m pip install -U pip

tensorboard/data/server/Cargo.toml

@@ -46,13 +46,14 @@ serde_json = "1.0.59"
 thiserror = "1.0.21"
 tokio = { version = "1.0.2", features = ["macros", "rt-multi-thread"] }
 tokio-stream = { version = "0.1.2", features = ["net"] }
-tonic = "0.4.0"
+tonic = "0.4.2"
+tonic-reflection = "0.1.0"
 walkdir = "2.3.1"
 
 [dev-dependencies]
 prost-build = "0.7.0"
 tempfile = "3.1.0"
-tonic-build = "0.4.0"
+tonic-build = "0.4.2"
 
 [[bin]]
 name = "rustboard"
@@ -113,3 +114,13 @@ additional_flags = [
 
 [package.metadata.raze.crates.prost-build.'0.7.0']
 gen_buildrs = true
+
+[package.metadata.raze.crates.tonic-reflection.'0.1.0']
+gen_buildrs = true
+build_data_dependencies = ["@com_google_protobuf//:protoc"]
+
+[package.metadata.raze.crates.tonic-reflection.'0.1.0'.buildrs_additional_environment_variables]
+PROTOC = "$(execpath @com_google_protobuf//:protoc)"
+# We don't have easy access to a rustfmt binary, so make it a no-op.
+# https://github.com/bazelbuild/rules_rust/issues/87
+RUSTFMT = "/bin/true"

tensorboard/data/server/cargo/BUILD.bazel

@@ -230,7 +230,7 @@ alias(
 
 alias(
     name = "tonic",
-    actual = "@raze__tonic__0_4_0//:tonic",
+    actual = "@raze__tonic__0_4_2//:tonic",
     tags = [
         "cargo-raze",
         "manual",
@@ -239,7 +239,16 @@ alias(
 
 alias(
     name = "tonic_build",
-    actual = "@raze__tonic_build__0_4_0//:tonic_build",
+    actual = "@raze__tonic_build__0_4_2//:tonic_build",
+    tags = [
+        "cargo-raze",
+        "manual",
+    ],
+)
+
+alias(
+    name = "tonic_reflection",
+    actual = "@raze__tonic_reflection__0_1_0//:tonic_reflection",
     tags = [
         "cargo-raze",
         "manual",