services/horizon: Decouple reaping module from Horizon App

[urvisavla]

What problem does your feature solve?

Eliminate the Horizon App dependency for the 'reap' command.

What would you like to see?

Presently, the reap command initializes the Horizon app with all the flags, which triggers captive core config setup due to the RequireCaptiveCoreConfig flag being set to true (and ingestion is set to true by default). However, the reaping module should be independent of captive core dependencies and solely rely on the --db-url and --history-retention-count flags for the reaping operation.

What alternatives are there?

N/A