[feature/reduce-mem-footprint] Reduce memory footprint

[felix-schwarz]

based on #1351 until that is merged

Description

In this PR:

• reduced memory consumption of the File Provider by removing dependency on ownCloudApp and its dependencies (like OpenSSL.framework). This increases the amount of memory available to the File Provider after loading, thereby also improving stability.
• avoid use of FileProvider via XPC due to stability issues
  • [x] by Media Import
  • [ ] by Share Extension
  • [ ] by SaveFileIntent (Apple Shortcuts integration)
• fix spurious "invalid parameter" error on import in File Provider
• properly clean up status of ProgressSummarizer after disconnect

Paired with https://github.com/owncloud/ios-sdk/pull/110.

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

[CLAassistant]

All committers have signed the CLA.