[Partial fix for #1372]Added SimpleTypesExcludeFilter to exlcude validat...

...ion on simple types and also added tests to cover scenarios.

@yishaigalatzer @pranavkm @rynowak @harshgMSFT 

Note:
- This PR does not have comments. I will add them once we agree upon the changes.
`underlyngType` -> `underlyingType` you can see that `Nullable.GetUnderlyingType` spells it correctly :laughing: