Fix parsing of ignored operators in websearch_to_tsquery().

Fix parsing of ignored operators in websearch_to_tsquery().

The manual says clearly that punctuation in the input of
websearch_to_tsquery() is ignored, except for the special cases
of dashes and quotes.  However, this failed for cases like
"(foo bar) or something", or in general an ISOPERATOR character
in front of the "or".  We'd switch back to WAITOPERAND state,
then ignore the operator character while remaining in that state,
and then reach the "or" in WAITOPERAND state which (intentionally)
makes us treat it as data.

The fix is simple enough: if we see an ISOPERATOR character while in
WAITOPERATOR state, we have to skip it while staying in that state.
(We don't need to worry about other punctuation characters: those will
be consumed as though they were words, but then rejected by lexizing.)

In v14 and up (since commit eb086056f) we can simplify the code a bit
more too, because there is no longer a reason for the WAITOPERAND
state to distinguish between quoted and unquoted operands.

Per bug #18479 from Manos Emmanouilidis.  Back-patch to all supported
branches.

Discussion: https://postgr.es/m/18479-d9b46e2fc242c33e@postgresql.org