Support command and args

[yandongxiao]

Describe the problem

Although the Operator currently supports two extension methods, Init Container and sidecar, they may not meet users' needs in some situations.

1. Users need to extend the Entrypoint script. For example, users may want to dynamically export some environment variables based on runtime information. In this case, users need to create their own Dockerfile and build their own container image.
2. Users wish to add some files to the container. For instance, they may want to add a jar file to the lib directory. If the size of the jar file exceeds 1MB, users must first create a shared volume, then copy the existing contents of the lib directory to the shared volume, and finally mount this volume to the lib directory.

Describe the solution you'd like

Although users can find workarounds, that increases the complexity of their operations.

We can solve the above problems by supporting the command and args field.