A number of tokenfilters can produce multiple tokens at the same position. This
is a problem when using token chains to parse synonym files, as the SynonymMap
requires that there are no stacked tokens in its input.
This commit ensures that when used to parse synonyms, these tokenfilters either produce
a single version of their input token, or that they throw an error when mappings are
generated. In indexes created in elasticsearch 6.x deprecation warnings are emitted in place
of the error.
* asciifolding and cjk_bigram produce only the folded or bigrammed token
* decompounders, synonyms and keyword_repeat are skipped
* n-grams, word-delimiter-filter, multiplexer, fingerprint and phonetic throw errors
Fixes#34298
a646f85a99