feature: auto de-duplication of plugin configs during dump

decK should be able to automatically de-duplicate configuration of multiple plugin instances of same type.

#93 implements de-duplication in the file but a user has to manually create the file or move the relevant pieces in the YAML source.

With this feature, de-duplication would happen automatically.

Such a feature helps in maintenance, where a user can simply edit the configuration in one place, instead of repeating.

Start by reviewing issue #93 and the dump flow that writes the YAML source, since no specific files or tests are named here. Define the de-duplication behavior for multiple plugin instances of the same type and verify that dumping produces shared configuration automatically without requiring manual file edits.

Written by the indexing model from the issue text.