openapi3: use Ptr instead of BoolPtr,Float64Ptr,Int64Ptr,Uint64Ptr

[alexandear]

This adds generic openapi3.Ptr function to be used instead of openapi3.BoolPtr, openapi3.Float64Ptr, openapi3.Int64Ptr, openapi3.Uint64Ptr.

[fenollp]

I fail to see the improvement here. Today's explicitly typed functions make it much easier to grasp their purpose and to find IMO. Thoughts?

[alexandear]

I fail to see the improvement here. Today's explicitly typed functions make it much easier to grasp their purpose and to find IMO. Thoughts?

I intend to introduce' Ptr' to shorten BoolPtr, Float64Ptr, Int64Ptr, Uint64Ptr. Fewer symbols - same meaning. And this reduces the number of functions to remember for the library users.

See these PRs where Ptr was recently introduced:

• Add Ptr function to use generics for allocating pointers xanzy/go-gitlab#1788
• feat: Deprecate and replace Bool,Int,Int64,String with Ptr using generics google/go-github#3355 (not yet merged, but likely to be merged soon)