Summary:
We had recently started avoiding caching data in block cache read by intent iterators for CDC. This [[ https://phorge.dev.yugabyte.com/D40487 | change ]] was guarded under flag `cdc_cache_intent_block`. As part of this diff, we are changing two things:
1. Rename flag to `cdc_enable_caching_db_block` to make it general purpose incase we want to extend it usage to regularDB.
2. Change default flag value to true to enable caching in block cache
Jira: DB-14826

Test Plan: Jenkins

Reviewers: skumar, sumukh.phalgaonkar

Reviewed By: sumukh.phalgaonkar

Subscribers: ybase

Tags: #jenkins-ready

Differential Revision: https://phorge.dev.yugabyte.com/D41125