Rename IModelFinalizedConvention to IModelFinalizingConvention

[AndriySvyryd]

Introduce IModelFinalizedConvention that don't change the model

Part of #12846

[smitpatel]

[ajcvickers]

@AndriySvyryd Motivation for changing the name here? Is it purely to make the name more "correct" or do we functionally need to change?

[AndriySvyryd]

@ajcvickers We need to have conventions that run after the OnModelFinalized conventions for two reasons:

1. Moving ValidatingConvention there will make it easier for providers and users to add conventions as they need to run before ValidatingConvention
2. We need a hook for model transformations that don't change the configuration, such as adding a relational model or switching to a runtime-optimized implementation.