backend: Use features for opendal services

[aawsome]

No description provided.

[aawsome]

@simonsan Can you have a look at this PR? The tests currently fails as we'd need to adapt the CI pipelines to use the ci feature instead of all features. I like to have your thoughts first before starting to adapt the pipeline.

[mro68]

Hi! Just wanted to link some related work that might be of interest:

Google Drive Performance Optimization PRs

We've been working on making Google Drive a viable backend for rustic, and have submitted:

1. fix(backend/opendal): include scheme in location() for backend identification #444 - fix(backend/opendal): include scheme in location()

   • Small fix to include the OpenDAL scheme in location() output
   • Needed for backend-specific optimizations

2. feat(core): add PackCachingBackend for API-expensive backends like GDrive #445 - feat(core): add PackCachingBackend for GDrive

   • LRU cache for pack files to avoid repeated API calls
   • Makes forget --prune actually work on GDrive (was crashing before)
   • ~45x faster repoinfo, ~50x faster directory listing

These work together with an OpenDAL PR (apache/opendal#7059) that implements batch recursive listing for GDrive.

The feature refactoring in this PR (#417) looks great and should make it easier to enable/disable specific backends like gdrive! 👍