Add an in memory credential providers

[mbenita-Cyberark]

Is your feature request related to a problem? Please describe.

Currently we have two keystore for the CLI and Client. these are Keystore and FileCredentialProvider. While working with the Cli these are two sufficient solutions. The SDK can use a better and more secure Provider, which is a simply in memory credential provider. which holds the api-key and the rest of credentials data in memory for as long as the app running

Describe the solution you would like

Create a simple CredentialProvider implementing CredentialsStoreInterface. The Client should accept CredentialsStoreInterface instance as a parameter. this way the user can decide which CredentialProvider to use. This means we need to expose our factory method outside as well. so the user could inject the right instance

Describe alternatives you have considered

Additional context

Add any other context information about the feature request here.