[Feature Request] provide an option to disable messages sent to ERROR

(check apply)
- [x] read [the contribution guideline](https://github.com/uken/fluent-plugin-elasticsearch/blob/master/CONTRIBUTING.md)

**Is your feature request related to a problem? Please describe.**

In environment's with high rates of poorly constructed messages, where OpenSearch is rejected many messages, the plugin will flood out logging about the 4xx events for each poorly constructed message.

While log_os_400_reason is available to tune down the verbosity of the individual messages, it still makes an error log for each message rejected by OpenSearch

example:
`2022-03-19 16:59:08 +0000 [warn]: #0 send an error event to @ERROR: error_class=Fluent::Plugin::OpenSearchErrorHandler::OpenSearchError error="400 - Rejected by OpenSearch" location=nil tag="" time=2022-03-19 16:59:06.948702500 +0000`

**Describe the solution you'd like**

provide an option to disable messages sent to ERROR (or if considering this [feature request](https://github.com/fluent/fluent-plugin-opensearch/issues/35), wherever the message is sent to)

**Describe alternatives you've considered**

Tried tuning down messages from the plugin using the system ignore_repeated_log_interval and ignore_same_log_interval options, but those did not stop any of the aforementioned messages. That is probably due to each message having a unique timestamp, etc..