Add function body for Gelu and FastGelu (#7496)
* LayerNorm function body v1
* LayerNorm function body
* layernorm function test
* Minor fixes
* Fix signed unsigned comparison
* Move contrib ops test
* Handle optional output parameters
* Add test case for optional outputs
* Handle float16 random generation
* Add function body to Gelu and FastGelu
* Add FastGelu test
* Fix comments
* Include cmath
