0.12.2

• Move the instance field TypeValidatorBase._shouldBeComparedToNull to a static readonly field (renamed to _canBeNull) to cache the reflection result per TypeValidatorBase<T> type and eliminate redundant per-instance evaluations.
• Remove the eagerly allocated NotNullValidationMessageProvider during ExpressValidatorBuilder configuration, and instantiate NotNullValidationMessageProvider<object, T> only when the value is null.
  Deprecate NotNullValidationMessageProvider.GetMessage(ValidationContext<T>).
• Update to FluentValidation 12.1.0.
• Rename private TypeValidatorBase.HasOnlyNullOrEmptyValidators to HasNonEmptyValidators (inverting the boolean logic) and remove the negation of this property in the ShouldValidate method.
• DRY refactor of null validation in TypeValidatorBase<T>.
• Add tests for null-tolerance validation in QuickValidator.
• Add test for validating a primitive type using ExpressValidatorBuilder.
• Add a unit test that verifies ExpressValidator does not throw when members are null and no null-related validators are used.
• Edit README.md and NuGet.md.