docs: Update README files for RDS multitenant module

- Add CloudWatch Database Insights for multi-tenant cost allocation to main README
- Update data-collection README with comprehensive RDS multitenant module documentation
- Use correct CloudWatch Database Insights terminology (replacing deprecated Performance Insights naming)
- Include module details, supported engines, key features, and prerequisites

Author: davidecoccia

README.md

@@ -24,7 +24,7 @@ This repository is a part of [Cloud Intelligence Dashboards](https://docs.aws.am
 
 This repository contains following elements:
 * [data-exports](/data-exports) - a Cloud Formation Templates for AWS Data Exports, such as Cost and Usage Report 2.0 and others. This allows a replication of Exports from your Management Account(s) to a Dedicated Data Collection Accounts as well as aggregation of multiple Exports from a set of Linked Accounts.
-* [data-collection](/data-collection) - a set of Cloud Formation Templates for collecting infrastructure operational data from Management and Linked Accounts. Such as data from AWS Trusted Advisor, AWS Compute Optimizer, Inventories, Pricing, AWS Health, AWS Support Cases etc. See more about types of data collected [here](/data-collection).
+* [data-collection](/data-collection) - a set of Cloud Formation Templates for collecting infrastructure operational data from Management and Linked Accounts. Such as data from AWS Trusted Advisor, AWS Compute Optimizer, Inventories, Pricing, AWS Health, AWS Support Cases, CloudWatch Database Insights, etc. See more about types of data collected [here](/data-collection).
 * [case-summarization](/case-summarization) - an additional Cloud Formation Template for deploying the AWS Support Case Summarization plugin that offers the capability to summarize cases through Generative AI powered by Amazon Bedrock.
 * [rls](/rls) - a stack for managing Row Level Security for CID Dashboards.
 * [security-hub](/security-hub) - Collection of data from AWS Security Hub.

data-collection/README.md

@@ -44,7 +44,7 @@ List of modules and objects collected:
 | `quicksight`                 |  [Amazon QuickSight](https://aws.amazon.com/quicksight/)    | Data Collection Account | Collects QuickSight User and Group information in the Data Collection Account only |
 | `resilience-hub`                 |   [AWS Resilince Hub](https://aws.amazon.com/resilience-hub/) | Linked Accounts |  |
 | `reference`                 |   Various services      | Data Collection Account | Collects reference data for other modules and dashboard to function |
-| `rds-multitenant`           |  [Amazon RDS](https://aws.amazon.com/rds/) | Linked Accounts | Collects Performance Insights metrics for multi-tenant RDS instances to enable cost allocation by tenant |
+| `rds-multitenant`           |  [Amazon RDS](https://aws.amazon.com/rds/) | Linked Accounts | Collects CloudWatch Database Insights metrics for multi-tenant RDS instances to enable cost allocation by tenant |
 
 ### Deployment Overview
 
@@ -59,6 +59,5 @@ For deployment and further information please reference to this [documentation](
 
 [![Documentation](/.images/documentation.svg)](https://docs.aws.amazon.com/guidance/latest/cloud-intelligence-dashboards/data-exports.html)
 
-
 ### Contributing
 See [CONTRIBUTING.md](CONTRIBUTING.md)