Make it easier to get an IntPtr from a *int

[lukehoban]

Today, the only conversion function available to create an IntPtr accepts an int, not a *int. This makes it quite awkward to accept pointers as input and construct IntPtr values - the code must manually nil-check the input, and then also there is no easy way (or perhaps even no way at all?) to inject the nil value into the pointer from user code.

The current pulumi.IntPtr function looks like:

// IntPtr is an input type for *int values.
func IntPtr(v int) IntPtrInput {
	return (*intPtr)(&v)
}

Of all the "projection" functions available to create Pulumi Output values from raw values, this is the only example where the projection input is not the same as the element type. I expect this was a mistake, as I cannot think of any reason it would have been necessary, and is significantly less flexible.

We should add an option that accepts a *int. Since we can't break existing code, we may have to name it something like IntPtrFromPtr.

Everything above applies for all pulumi.*Ptr projection functions - not just Int.

Note though that SDK codegen get this "right" - and generates projection functions from pointer types. It is only the core pulumi SDK primitives that have this "wrong".

func BucketObjectLockConfigurationPtr(v *BucketObjectLockConfigurationArgs) BucketObjectLockConfigurationPtrInput {
	return (*bucketObjectLockConfigurationPtrType)(v)
}