Updated tokenizer to better matching when search for code snippets (#32261)

This PR improves the accuracy of Gitea's code search. 

Currently, Gitea does not consider statements such as
`onsole.log("hello")` as hits when the user searches for `log`. The
culprit is how both ES and Bleve are tokenizing the file contents (in
both cases, `console.log` is a whole token).

In ES' case, we changed the tokenizer to
[simple_pattern_split](https://www.elastic.co/guide/en/elasticsearch/reference/current/analysis-simplepatternsplit-tokenizer.html#:~:text=The%20simple_pattern_split%20tokenizer%20uses%20a,the%20tokenization%20is%20generally%20faster.).
In such a case, tokens are words formed by digits and letters. In
Bleve's case, it employs a
[letter](https://blevesearch.com/docs/Tokenizers/) tokenizer.

Resolves #32220

---------

Signed-off-by: Bruno Sofiato <bruno.sofiato@gmail.com>

modules/indexer/internal/bleve/util_test.go

@@ -35,6 +35,14 @@ func TestBleveGuessFuzzinessByKeyword(t *testing.T) {
 			Input:     "갃갃갃",
 			Fuzziness: 0,
 		},
+		{
+			Input:     "repo1",
+			Fuzziness: 0,
+		},
+		{
+			Input:     "avocado.md",
+			Fuzziness: 0,
+		},
 	}
 
 	for _, scenario := range scenarios {