Refactor KeystoreUtils

[hwupathum]

Summary

This pull request includes several changes to the KeystoreUtils class in the org.wso2.carbon.utils package. The changes focus on updating how the default file type for keystores is handled and improving error handling for unsupported file types.

Key changes include:

Default File Type Handling:

• Removed the FALLBACK_TENANTED_KEYSTORE_FILE_TYPE constant and updated the defaultFileType method to return JKS.name() instead. [1] [2]
• Removed the defaultFileType constant from the StoreFileType enum.

Error Handling and Logic Improvement:

• Updated the getKeyStoreFileType method to handle the super tenant domain name case separately and added improved error logging for unsupported file types.
• Updated the getKeystoreInstance method to use StoreFileType.PKCS12.name() for comparison instead of the removed defaultFileType constant.