Patch in exact search for meilisearch (#29671)

meilisearch does not have an search option to contorl fuzzynes per query
right now:
 - https://github.com/meilisearch/meilisearch/issues/1192
 - https://github.com/orgs/meilisearch/discussions/377
 - https://github.com/meilisearch/meilisearch/discussions/1096

so we have to create a workaround by post-filter the search result in
gitea until this is addressed.

For future works I added an option in backend only atm, to enable
fuzzynes for issue indexer too.
And also refactored the code so the fuzzy option is equal in logic to
code indexer


---
*Sponsored by Kithara Software GmbH*

modules/indexer/code/indexer_test.go

@@ -70,7 +70,7 @@ func testIndexer(name string, t *testing.T, indexer internal.Indexer) {
 
 		for _, kw := range keywords {
 			t.Run(kw.Keyword, func(t *testing.T) {
-				total, res, langs, err := indexer.Search(context.TODO(), kw.RepoIDs, "", kw.Keyword, 1, 10, false)
+				total, res, langs, err := indexer.Search(context.TODO(), kw.RepoIDs, "", kw.Keyword, 1, 10, true)
 				assert.NoError(t, err)
 				assert.Len(t, kw.IDs, int(total))
 				assert.Len(t, langs, kw.Langs)