Describe the pull request

This PR implements support for memory budgets using the new AllocationBehavior flags, that can be passed to the IGraphicsFactory methods that allocate resources. The first of those flags, StayWithinBudget forces allocations to fail, if no more memory is available in a given resource heap and it is not possible to allocate more. Drivers may fall back to allocating memory from a different (less efficient) heap instead, but with this new flag, clients have control over this behavior. The second flag, DontExpandCache is even more strict, as it prevents the underlying allocators from allocating additional heap space altogether. This can be useful in performance critical code, where allocations can be postponed to a later (less critical) time.

By default, the factory methods previously raised an exception, if allocations failed. Especially to be used in combination with the new budgeting flags, resource factory methods now provide a version prefixed with try (e.g., IGraphicsFactory::tryCreateBuffer), that does not fail, but returns a boolean instead. Note that those methods may still raise exceptions, if input argument validation fails, however, they do no longer throw if the allocation itself fails.

Related issues

• Resolves Implement memory budgets. #177