add Get/Set LoD in InfershapeContext

[jacquesqiao]

reason

InfershapeContext is used to do Shape inference, LoD is part of shape, now we have ShareLoD in InfershapeContext, but can not get or set LoD directly, so we need to add these interface to InfershapeContext.

implementation

For compile time infershape, we can only get the level of lod, so we do not support Get/Set LoD during CompileTime Infershape.
For RunTime infershape, we think GetLod is used to get the LoD of input and SetLod can only set the LoD of output.