feat(widget): add strict graph widgets (#164)

Introducing new specialized graph widget classes. They have customized input props which force user to be consistent in how they use the graph. For example, about the number of axes. It will also force user to provide axis description. One tiny improvement is that for single-metri widgets, we will not show the legend, saving some valuabe space.

These new widgets will be used in the monitoring classes instead of plain GraphWidgets to make sure they are all properly defined.

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