Add support for some form struct based agent addon

[saswatamcode]

I would like to propose an idea for something like BuildStructAgentAddon, that takes in some interface{} which implements a Manifests() method which has default values and values you can pass in.

Essentially a downstream operator could just maintain the objects they manage as k8s structs instead of helm or Go templates, so such a function, makes it much easier for those operators to create agent addons based on pre-existing code. Also, has added benefit that linting/updating manifests/managing versions in Go is much easier.