feat: add default batch timeout of 5s

[obs-gh-mattcotter]

Description

Add default batch timeout of 5s to reduce number of requests.

Checklist

• Created tests which fail without the change (if possible)
• Extended the README / documentation, if necessary

[obs-gh-jabernet]

https://docs.observeinc.com/en/latest/content/data-ingestion/endpoints/otel.html ; Our per request limit is 50mb uncompressed. So we could have significantly higher thresholds assuming 1kb log lines. Maybe we should just set both values to the default send_batch_size of 8192 for now and we can tune it in another PR based on data from O2?

[obs-gh-mattcotter]

https://docs.observeinc.com/en/latest/content/data-ingestion/endpoints/otel.html ; Our per request limit is 50mb uncompressed. So we could have significantly higher thresholds assuming 1kb log lines. Maybe we should just set both values to the default send_batch_size of 8192 for now and we can tune it in another PR based on data from O2?

I have updated this PR to only set the timeout and leave the sizing values as default. Thanks!