Fix for gitea putting everything into one request without batching and
sending it to Elasticsearch for indexing as issued in #28117
This issue occured in large repositories while Gitea tries to
index the code using ElasticSearch.
I've applied necessary changes that takes batch length from below config
(app.ini)
```
[queue.code_indexer]
BATCH_LENGTH=<length_int>
```
and batches all requests to Elasticsearch in chunks as configured in the
above config
(cherry picked from commit 5c0fc9087211f01375f208d679a1e6de0685320c)
00370f17a4