Rename {Create,Lazy}TokenStream as {To,Lazy}AttrTokenStream.

`To` is better than `Create` for indicating that this is a non-consuming
conversion, rather than creating something out of nothing.

And the addition of `Attr` is because the current names makes them sound
like they relate to `TokenStream`, but really they relate to
`AttrTokenStream`.

compiler/rustc_parse/src/parser/mod.rs

@@ -237,7 +237,7 @@ struct TokenCursor {
     // the trailing `>>` token. The `break_last_token`
     // field is used to track this token - it gets
     // appended to the captured stream when
-    // we evaluate a `LazyTokenStream`
+    // we evaluate a `LazyAttrTokenStream`.
     break_last_token: bool,
 }
 
@@ -1465,7 +1465,7 @@ pub fn emit_unclosed_delims(unclosed_delims: &mut Vec<UnmatchedBrace>, sess: &Pa
 }
 
 /// A helper struct used when building an `AttrTokenStream` from
-/// a `LazyTokenStream`. Both delimiter and non-delimited tokens
+/// a `LazyAttrTokenStream`. Both delimiter and non-delimited tokens
 /// are stored as `FlatToken::Token`. A vector of `FlatToken`s
 /// is then 'parsed' to build up an `AttrTokenStream` with nested
 /// `AttrTokenTree::Delimited` tokens.