chore(rds): Upgrade MySQL engine version to 8.4.5

[jongwooo]

This pull request updates the RDS module configuration to support a newer MySQL engine version and includes changes to improve naming consistency and enable major version upgrades.

Updates to RDS configuration:

• Updated the MySQL engine version from 8.0.40 to 8.4.5 in the aws_db_instance resource to use a newer version of MySQL.
• Enabled the allow_major_version_upgrade option in the aws_db_instance resource to permit future major version upgrades.

Naming consistency improvements:

• Renamed the aws_db_parameter_group resource from db_params to db_parameter_group for better clarity and consistency.
• Updated the parameter_group_name reference in the aws_db_instance resource to match the new parameter group name.
• Changed the family attribute of the aws_db_parameter_group resource from mysql8.0 to mysql8.4 to align with the updated MySQL engine version.

[Copilot]

Pull Request Overview

This PR updates the RDS module to use MySQL engine version 8.4.5 and improves naming consistency for the database parameter group resource.

• Updates MySQL engine version from 8.0.40 to 8.4.5
• Enables major version upgrades for the RDS instance
• Renames parameter group resource and related references for better clarity

Comments suppressed due to low confidence (1)

Modules/RDS/main.tf:13

• MySQL version 8.4.5 may not be a valid or available version in AWS RDS. The MySQL 8.4 series is relatively new and may not be generally available. Please verify that this specific version is supported by AWS RDS in your target region, as unsupported versions will cause deployment failures.

  engine_version              = "8.4.5"