refactor(nextcloud): reorganize package structure

[Leptopoda]

It's a bit messy around the webdav stuff, but I hope it's still reviewable.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 11 lines in your changes missing coverage. Please review.

Project coverage is 30.98%. Comparing base (ee0faea) to head (43dcdcb).
Report is 9 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2295   +/-   ##
=======================================
  Coverage   30.98%   30.98%           
=======================================
  Files         265      268    +3     
  Lines       96721    96721           
=======================================
  Hits        29966    29966           
  Misses      66755    66755           

Flag	Coverage Δ		*Carryforward flag
cookie_store	90.51% <ø> (ø)		Carriedforward from ee0faea
dynamite	31.10% <ø> (ø)		Carriedforward from ee0faea
dynamite_end_to_end_test	60.03% <ø> (ø)		Carriedforward from ee0faea
dynamite_runtime	85.40% <ø> (ø)		Carriedforward from ee0faea
neon_dashboard	96.20% <ø> (ø)
neon_framework	45.90% <ø> (ø)
neon_notifications	100.00% <ø> (ø)
neon_talk	98.18% <ø> (ø)
nextcloud	27.73% <66.66%> (ø)
sort_box	90.90% <ø> (ø)		Carriedforward from ee0faea

*This pull request uses carry forward flags. Click here to find out more.

Files	Coverage Δ
...xtcloud/lib/src/api/cookbook/cookbook.openapi.dart	95.45% <ø> (ø)
...cloud/lib/src/api/cookbook/cookbook.openapi.g.dart	49.21% <ø> (ø)
...xtcloud/lib/src/api/cookbook/cookbook_helpers.dart	100.00% <ø> (ø)
...kages/nextcloud/lib/src/api/core/core.openapi.dart	47.93% <ø> (ø)
...ges/nextcloud/lib/src/api/core/core.openapi.g.dart	28.95% <ø> (ø)
...kages/nextcloud/lib/src/api/core/core_helpers.dart	100.00% <ø> (ø)
...cloud/lib/src/api/dashboard/dashboard.openapi.dart	97.28% <ø> (ø)
...oud/lib/src/api/dashboard/dashboard.openapi.g.dart	51.06% <ø> (ø)
...kages/nextcloud/lib/src/api/news/news.openapi.dart	95.09% <ø> (ø)
...ges/nextcloud/lib/src/api/news/news.openapi.g.dart	39.95% <ø> (ø)
... and 33 more

[provokateurin]

So much better than before :)