Package rust-docs-json into nightly components (take 3)

`dist` creates a `rust-docs-json.tar.xz` tarfile. But build-manifest expected it to be named
`rust-docs-json-preview.tar.xz`. Change build-manifest to allow the name without the `-preview` suffix.

This also adds `rust-docs-json` to the `rust` component. I'm not quite sure why it exists,
but rustup uses it to determine which components are available.

src/bootstrap/dist.rs

@@ -1365,6 +1365,7 @@ impl Step for Extended {
         }
 
         add_component!("rust-docs" => Docs { host: target });
+        add_component!("rust-json-docs" => JsonDocs { host: target });
         add_component!("rust-demangler"=> RustDemangler { compiler, target });
         add_component!("cargo" => Cargo { compiler, target });
         add_component!("rustfmt" => Rustfmt { compiler, target });

src/tools/build-manifest/src/main.rs

@@ -437,7 +437,7 @@ impl Builder {
             host_component("rustfmt-preview"),
             host_component("llvm-tools-preview"),
             host_component("rust-analysis"),
-            host_component("rust-docs-json"),
+            host_component("rust-docs-json-preview"),
         ]);
 
         extensions.extend(

src/tools/build-manifest/src/versions.rs

@@ -20,6 +20,7 @@ pub(crate) enum PkgType {
     Rustfmt,
     LlvmTools,
     Miri,
+    JsonDocs,
     Other(String),
 }
 
@@ -36,6 +37,7 @@ impl PkgType {
             "rustfmt" | "rustfmt-preview" => PkgType::Rustfmt,
             "llvm-tools" | "llvm-tools-preview" => PkgType::LlvmTools,
             "miri" | "miri-preview" => PkgType::Miri,
+            "rust-docs-json" | "rust-docs-json-preview" => PkgType::JsonDocs,
             other => PkgType::Other(other.into()),
         }
     }
@@ -53,6 +55,7 @@ impl PkgType {
             PkgType::Rustfmt => "rustfmt",
             PkgType::LlvmTools => "llvm-tools",
             PkgType::Miri => "miri",
+            PkgType::JsonDocs => "rust-docs-json",
             PkgType::Other(component) => component,
         }
     }
@@ -72,6 +75,7 @@ impl PkgType {
             PkgType::Rust => true,
             PkgType::RustSrc => true,
             PkgType::Rustc => true,
+            PkgType::JsonDocs => true,
             PkgType::Other(_) => true,
         }
     }