16918: Correct configuration schema errors

[jastraat]

Currently both search_api.index.dkan and system.action.hide_current return schema errors when running the following check:

drush config:inspect --strict-validation

• Test coverage exists
• Documentation exists

QA Steps

• Temporarily install the config_inspector contributed module
• Run drush config:inspect --strict-validation and confirm no schema errors for DKAN-related configuration files.

[paul-m]

The changes generalize the views config, and only strengthen the schema for other configs.