Revisit "enabled" properties for view technologies

[bclozel]

As seen in #32162, spring.${viewTechnology}.enabled properties do not disable entirely the auto-configuration, but rather controls the registration of the MVC/WebFlux component that resolves templates for web views.

This applies to Freemarker, Thymeleaf and Mustache (and possibly others).

We should revisit this situation and choose between:

• renaming the properties to align them with the current behavior
• consider changing the behavior

In other situations, we've tried not to link an *.enabled property with auto-configurations being applied.