enhance aggregation and timeseries documentation with query block cacheUpdate query cache docs

[dharshini-2007]

Summary

This PR improves the documentation for Timeseries and Aggregations in the Graph Node project.
It adds detailed explanations, examples, and introduces the Query Block Cache section to help developers understand how caching works and how it improves query performance.

Changes

• Updated docs/aggregation.md with:
  • Timeseries and Aggregation schema examples
  • Aggregation functions and expression usage
  • Query examples with filters
  • Query Block Cache explanation, including modules reading/writing cache, configuration, and debugging tips

Motivation

Better documentation helps contributors and developers:

• Understand Timeseries and Aggregations structure
• Use aggregation functions correctly
• Optimize queries using the Query Block Cache

No code changes are included; this is a documentation-only update.

Checklist

• Documentation is clear and complete
• Examples are accurate and up-to-date