This is needed to continue to emit original terms so that the analysis chain behaves like ASCIIFolding with preserve_original when we'll use icu folsing.
|Resolved||debt||T132637 Lack of diacritic folding in e.g. Ancient Greek|
|Resolved||• dcausse||T137830 Use the icu_folding filter if available instead of asciifolding|
|Resolved||• dcausse||T138749 Add a generic preserve original token filter to the extra plugin|