Add bytes per second timing calculation for indexer

What does this MR do and why?

Related to #378307 (closed)

Introduce a new timing calculation to assess indexing health. This will allow us to see if the indexing is slowing down compared to the current method (a timer around the entire indexing process for each project) which is prone to report SLO violations when large projects get indexed in the initial or incremental queues (we have no control over this and it will occasionally experience spikes)

Screenshots or screen recordings

N/A

How to set up and validate locally

1. setup your gdk for elasticsearch and enable advanced search feature
2. import a large project
3. observe that indexed_bytes_per_second is reported in the log/elasticsearch.log file

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.