feat: Plugin Service & Host List Providers

[ColinKYuen]

Summary

Adds a plugin service to house common / shared resources & Host List Providers to provide and share topology updates

Description

• PluginService, houses common / shared resources between plugins
  • Moved TopologyService -> PluginService
• TopologyUtil, interface for getting topology, instance info, etc
  • ClusterTopologyHelper -> AuroraTopologyUtil
• HostListProvider, for plugins to retrieve a list of hosts
  • ClusterTopologyMonitor moved into -> RdsHostListProvider
• HostInfo is_writer flag changed to an enum
• Failover Plugin now uses HostListProviders and does not maintain the cluster monitor
• Minor renaming in OdbcHelper to avoid conflict with other defines, i.e. removing the SQL prefix in functions
• RdsLibLoader, removed module cleanup to resolve seg faults on improper cleanup order, delegating to OS to cleanup process

Testing

• Manual testing MySQL w/ Failover, IAM
• ODBC GUI Test button

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.