Add regular expression support to streaming search

Introduces an explicit regex query term node (which wraps an
RE2 regex instance internally) and extends the existing
UTF-8 flexible string searcher to use this query node.

Regex matching is optionally case (in)sensitive depending
on the normalization mode used.

Note on `searcher/searcher_test.cpp`: this adds a magic
sentinel `#` char prefix to query term parsing in the test
to let a query term be interpreted as a regex rather than
exact/prefix/suffix/substring match.

0 files changed, 0 insertions, 0 deletions