Single-schema-multi-kernel (#15184)
The PR is to allow custom op of different input types to have same op
name in a graph.
The idea to go over all ops of same name and merge their input/output
types into a type-inference function.
With the enhancement, custom op node inside a graph can have same
op-type given that the input/output types are different.
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Co-authored-by: Randy Shuai <rashuai@microsoft.com>
