refactor(bazel): shorten Rust toolchain names

bazel/BUILD

@@ -1,4 +1,4 @@
 exports_files([
-    "rust_toolchain.bzl",
+    "rust.bzl",
     "utils.bzl",
 ])

bazel/rust.bzl

@@ -126,7 +126,7 @@ rust_stdlib_filegroup(
 load("@rules_rust//rust:toolchain.bzl", "rust_toolchain")
 
 rust_toolchain(
-    name = "rust_toolchain_impl",
+    name = "toolchain_impl",
     rust_doc = ":rustdoc",
     rust_std = ":rust_std",
     rustc = ":rustc",
@@ -153,8 +153,8 @@ rust_toolchain(
 )
 
 toolchain(
-    name = "rust_toolchain",
-    toolchain = ":rust_toolchain_impl",
+    name = "rust",
+    toolchain = ":toolchain_impl",
     toolchain_type = "@rules_rust//rust:toolchain_type",
     visibility = ["//visibility:public"],
 )
@@ -172,7 +172,7 @@ rust_repository = repository_rule(
 
 
 def _rust_impl(module_ctx):
-    rust_repository(name = "rust_toolchain")
+    rust_repository(name = "rust")
 
 
 rust = module_extension(