Add Parallel Indexing

[PJColombo]

It depends on the following API changes.

This PR introduces parallel indexing by dividing the slots to be processed into manageable chunks, each of which is handled by a dedicated indexing thread.

To enhance error resilience during large-scale slot processing, an initial division of slots is performed. Each chunk is then processed sequentially. This approach allows for frequent updates to the latest slot and mitigates the need for extensive rollbacks in the event of a failure.

Additional modifications included in this PR:

• Context refactoring.
• Addition of local development tracing spans.
• Minor adjustments to the client's types.

Also, I attach the logs from a preliminary benchmark test, in which 1000 slots were indexed:

• Sequential indexing (~4 minutes and 39 seconds):

[2023-05-17T18:28:10.597Z]  INFO: blobscan_indexer/82110 on tallahassee: [SLOTS_PROCESSOR - END] (elapsed_milliseconds=279484,file=src/main.rs,final_slot=88000,initial_slot=87001,line=47,target=blob_indexer)

• Parallel indexing (~24 seconds)

[2023-05-17T18:35:45.750Z]  INFO: blobscan_indexer/85108 on tallahassee: [SLOTS_PROCESSOR - END] (elapsed_milliseconds=24255,file=src/main.rs,final_slot=88000,initial_slot=87001,line=47,target=blob_indexer)

There's a substantial improvement in speed, performing approximately 11.52 times faster than the sequential approach.

[PabloCastellano]

looks good! I'll try it today