EDStatic refactor and Prometheus FeatureFlag metrics

[ChrisJohnNOAA]

Description

This refactors messages and config out of EDStatic, both the fields and the parsing of the relevant files. It also adds @FeatureFlag annotation which is used in the new EDConfig to mark booleans that should be included in Prometheus metrics. This will allow admins and ERDDAP developers an easier time knowing what the config state of a server is.

Note this is based on the changes in #252 so that should be merged first.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist before requesting a review

• I have performed a self-review of my code
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works - almost entirely a refactor, so no new tests added
• New and existing unit tests pass locally with my changes