Auto merge of #25059 - erickt:pprint, r=acrichto

Auto merge of #25059 - erickt:pprint, r=acrichto

The recent quote changes unfortunately broke unquoting statements like `let foo = 5` because the parser requires their to be a trailing semicolon in those statements. Along the way I added support for unquoting generics and where clauses as well as better pretty printing of `token::Interpolated`.