Conduit: config variable naming conventions

[winder]

Review configuration variable names, i.e. "indexer-data-dir" for the block_processor shouldn't mention "indexer"

We are also inconsistent with the format, i.e. top level configurations are capitalized, while plugins are currently lower-kebab-case.

Acceptance Criteria

1. In block_processor: Change "indexer-data-dir" to "data-dir"
2. In the top level configurations, change to lower-kebab-case.
3. Stay with snake case for plugins, review the plugins and make as consistent as possible.