Codegen feature enablement in addition to the extension

[charles-lunarg]

A common bug I see is people enabling an extension but forgetting to enable the feature. It would be nice to have vk-bootstrap automate enabling the extension and the feature.

This may have to be hand written for some things, but since many extensions have 1 member feature structs, it seems like most could be generated.

Origin story: Helping coworker & others trying to enable the VK_EXT_shader_object extension using the extension layer, but the layer disables itself if the feature wasn't enabled, which leads to confusing issues if the driver doesn't error out when enabling an unsupported extension.