Allow target modules to define their own enforced configs

Problem/Motivation

We currently have a single global list of enforced configs. This currently breaks if it contains an enforced config in a target module that isn't yet enabled. More importantly, while the current functionality is handy for site builders, it should also prove quite useful for module maintainers.

Steps to reproduce

Create a target module and save some config into it. Disabling the module will then cause errors.

Proposed resolution

Split up config_enforce.enforced_configs.yml into multiple config_enforce.<module_name>.enforced_configs.yml

Remaining tasks

1. Write enforced config settings into target-module-specific configs
2. Compile enforced configs list from all target modules.

User interface changes

None.

API changes

API changes should be minimal and isolated to the ConfigEnforce and ConfigEnforceDevel classes, which handle reading and writing enforced configs.

Data model changes

The overall data model remains mostly unchanged, but the config storage will be altered. We may be able to remove a couple keys from storage, as the module name (at least), should be easy to populate from context.

We'll may also want to add a key to target module info.yml files to more easily identify them