[Features] reuse SchedulingPolicy struct for the scheduling policy defiinition of InstanceTemplate

[starnop]

What is the user interaction of your feature
A concise description of user interactions or user stories of your feature request

We support overwriting the common definitions of components in the InstanceTemplate. But right now, regarding scheduling configurations, the InstanceTemplate supports only partial scheduling configurations.
Maybe it's better to reuse SchedulingPolicy struct for the scheduling policy definition of InstanceTemplate.

Is your feature request related to a problem? Please describe.
A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]

If this is a new feature, please describe the motivation and goals.
A clear and concise description of why you want to happen, link the design doc if possible

Describe the solution you'd like
A clear and concise description of what you want to happen.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.