Move ExternalLocation to clean::types

It was previously defined in `render::search_index` but wasn't used at
all there. `clean::types` seems like a better fit since that's where
`ExternalCrate` is defined.

src/librustdoc/html/render/context.rs

@@ -14,7 +14,7 @@ use rustc_span::source_map::FileName;
 use rustc_span::symbol::sym;
 
 use super::print_item::{full_path, item_path, print_item};
-use super::search_index::{build_index, ExternalLocation};
+use super::search_index::build_index;
 use super::templates;
 use super::write_shared::write_shared;
 use super::{
@@ -22,7 +22,7 @@ use super::{
     BASIC_KEYWORDS,
 };
 
-use crate::clean::{self, ExternalCrate};
+use crate::clean::{self, types::ExternalLocation, ExternalCrate};
 use crate::config::RenderOptions;
 use crate::docfs::{DocFS, PathError};
 use crate::error::Error;