rustdoc-search: replace TAB/NL/LF with SP first

This way, most of the parsing code doesn't need to be designed to handle
it, since they should always be treated exactly the same anyhow.

tests/rustdoc-js-std/parser-errors.js

@@ -161,6 +161,15 @@ const PARSED = [
         userQuery: "a:: ::b",
         error: "Unexpected `:: ::`",
     },
+    {
+        query: "a::\t::b",
+        elems: [],
+        foundElems: 0,
+        original: "a:: ::b",
+        returned: [],
+        userQuery: "a:: ::b",
+        error: "Unexpected `:: ::`",
+    },
     {
         query: "a::b::",
         elems: [],