RDH check customization + minor improvements

• Adds an RDH version field to the custom checks that can be enabled through a TOML file.
• Processing now early exits if the first RDH0 deserialized from the raw data fails a generic sanity check.
• Enables experimental support for RDH versions above version 7. Now fastPASTA attempts to parse them as a generic RDH (with the features that are common to RDH v6 and v7).

Also contains some refactors to simplify initialization, reduce some boiler plate, and remove the ability to get the custom checks from a global static, has to be accessed through the global config instead.