Query: null semantics should apply to GreaterThanOrEqual, LessThanOrEqual, not only strict equality

This currently manifests in our translation of string.Contains:

SELECT [c].[FirstName]
FROM [FunkyCustomers] AS [c]
WHERE CHARINDEX(NULL, [c].[FirstName]) <= 0

we should be applying null semantics here instead:

SELECT [c].[FirstName]
FROM [FunkyCustomers] AS [c]
WHERE CHARINDEX(NULL, [c].[FirstName]) <= 0 OR CHARINDEX(NULL, [c].[FirstName]) IS NULL

[smitpatel]

If it is complicated then we can defer. Just wanted to bring this up if we are already fixing this.

[maumar]

Maybe we can look at it as a strech/investigation