Fix scalar sharing bug (#13299)
### Description
float and half initializers with same value are merged into same
initializer. This is a bug due to when we create pattern key, data type
is always be -1 (which is a naive mistake when doing code refactoring
previously), plus float and half are stored as float in constant store
for easier data comparison.
Added test coverage.
` [ONNXRuntimeError] : 1 : FAIL : Type Error: Type parameter (T) of
Optype (Mul) bound to different types (tensor(float) and tensor(float16)
in node
`
### Motivation and Context
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- If it fixes an open issue, please link to the issue here. -->
