feat(storagenode): support aws rds instance

[Xu-Wentao]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches

What this PR does / why we need it:

• support auto manage aws rds instance from StorageNode and DatabaseClass

---

there are some things need to be done in the future:

• Handle finalize resource logic, when instance is being deleting, we need to retain the storage node resource and waiting for instance be deleted.
• Enum aws instance status
• add more options for StorageNode annotations to set personal settings of DatabaseClass
  • masterUsername
  • generateMasterUserPassword and save the password to somewhere
  • some delete options like backup and snapshot
• add more test cases

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?

[mlycore]

LGTM

[mlycore]

Backup with snapshot is a key feature to StorageNode. Here's a new issue and let's discuss there.

[mlycore]

#317