[BUG] rename nodeSelector to masterNodeSelector

[cheyang]

What is your environment(Kubernetes version, Fluid version, etc.)

Describe the bug

Currently, we want to deploy master to specific node by using nodeSelector. I suggest to change it to masterNodeSelector which will not mislead the user.

nodeSelector:
                  additionalProperties:
                    type: string
                  description: NodeSelector is a selector which must be true for the
                    master to fit on a node
                  type: object

What you expect to happen:

How to reproduce it

Additional Information

[xieydd]

Any progress?