Add support for wildcard field type

This adds support for the "wildcard" field type that supports efficient
execution of wildcard and prefix queries by matching first against
trigrams (or bigrams or individual characters), then post-filtering by
evaluating the original field value against the pattern.

It also supports post-filtering by regexp queries, but doesn't yet have
an efficient first-phase approximation. (For general regex queries,
we'll probably never have a "good" first-phase approximation.)

Signed-off-by: Michael Froh <froh@amazon.com>

server/src/main/java/org/opensearch/index/mapper/KeywordFieldMapper.java

@@ -703,7 +703,7 @@ protected void parseCreateField(ParseContext context) throws IOException {
         }
     }
 
-    private static String normalizeValue(NamedAnalyzer normalizer, String field, String value) throws IOException {
+    static String normalizeValue(NamedAnalyzer normalizer, String field, String value) throws IOException {
         try (TokenStream ts = normalizer.tokenStream(field, value)) {
             final CharTermAttribute termAtt = ts.addAttribute(CharTermAttribute.class);
             ts.reset();