fix(rclone): support dependent remote config sections

[feelautom]

Summary

This fixes rclone wrapper remotes imported into Plakar when they depend on other rclone config sections.

For example, a crypt, alias, or chunker remote can reference another remote such as drive:bucket. Before this change, the connector installed only the imported wrapper section into rclone's in-memory config, so rclone could not resolve the dependent section and failed with errors such as:

failed to make remote "drive:bucket" to wrap: didn't find section in config file ("drive")

Changes

• Load existing rclone config sections into the in-memory config used by the connector.
• Override the active imported section with the Plakar store/source/destination configuration.
• Consume rclone_config_file / rclone_config as connector options instead of passing them to the backend.
• Keep the temporary config-file helper path compatible with dependent sections.
• Document the explicit config-file option for wrapper remotes.
• Add tests for dependent sections, explicit config file handling, and prefixed option normalization.

Validation

• GitHub Actions on fork passed for the full test/build branch before preparing this upstream-only branch.
• Runtime smoke-tested on Windows with a crypt remote backed by another remote:
  • plakar store ping succeeded.
  • plakar at @store create succeeded.
  • a small backup snapshot was created.
  • restore from that snapshot succeeded.

This PR branch intentionally excludes the temporary artifact-build workflow used for local validation, keeping the upstream diff focused on the rclone fix.

[omar-polo]

Hello,

Thanks for the PR. I'll do a proper review during the week. I've just realized that the first commits touch the utils package that I forgot to remove after the rclone rewrite, sorry if that brought some confusion ^^"

[feelautom]

Thanks for the clarification. I updated the PR to remove the changes touching the obsolete utils package and kept the fix focused on the current rclone connector path: in-memory config loading, connector option handling, tests, and README documentation.