Run config validation for config schema types opted in to be fully validatable

Problem/Motivation

This is a follow-up to #3402168: Follow-up for #3361534: Config validation errors can still occur for contrib modules, disrupting contrib and #3361534: KernelTestBase::$strictConfigSchema = TRUE and BrowserTestBase::$strictConfigSchema = TRUE do not actually strictly validate, per #3364109-49: Configuration schema & required values: add test coverage for `nullable: true` validation support.

Once #3364109: Configuration schema & required values: add test coverage for `nullable: true` validation support lands, we'll have a reliable mechanism to detect which config schema types (i.e. simple config objects or config entity types) are fully validatable.

The changes #3402168: Follow-up for #3361534: Config validation errors can still occur for contrib modules, disrupting contrib made should still be respected: we do NOT want config validation to be executed for every contrib module.

But we DO want run config validation for contrib modules when:

• validating a config schema type that has the FullyValidatable constraint
• that means that public function checkConfigSchema(TypedConfigManagerInterface $typed_config, $config_name, $config_data … has the FullyValidatable constraint as one of the values of $typed_config->getConstraints()

Steps to reproduce

N/A

Proposed resolution

TBD

Remaining tasks

TBD

User interface changes

TBD

API changes

TBD

Data model changes

TBD

Release notes snippet

TBD