VENOM-407: Add partial persistency

[naxuroqa]

• Add SqliteDhtNodeRepository, an improved storage for dht nodes
• Add SqliteNospamRepository, a storage for past nospams
• Add SqliteContactRepository, a storage for contact settings
• Add SqliteFriendRequestRepository, a storage for pending friend requests
• Add widgets to access previous nospams
• Add functionality to update dht nodes to settings widget
• Restore previous friend requests on startup
• Add cleanup of leftover files to flatpak manifest
• Update POTFILES

[codecov-io]

Codecov Report

Merging #419 into develop will decrease coverage by 1.01%. The diff coverage is 11.2%.

@@            Coverage Diff             @@
##           develop    #419      +/-   ##
==========================================
- Coverage     8.27%   7.26%   -1.02%     
==========================================
  Files           75      76       +1     
  Lines         4749    4999     +250     
==========================================
- Hits           393     363      -30     
- Misses        4356    4636     +280

Impacted Files	Coverage Δ
src/view/UserInfoWidget.vala	0% <0%> (ø)	:arrow_up:
src/tox/SqliteDhtNodeRepository.vala	0% <0%> (ø)
src/tox/DhtNode.vala	0% <0%> (ø)	:arrow_up:
src/view/FriendRequestWidget.vala	0% <0%> (ø)	:arrow_up:
src/tox/SqliteFriendRequestRepository.vala	0% <0%> (ø)
src/tox/ContactRepository.vala	0% <0%> (ø)
src/view/NodeWidget.vala	0% <0%> (ø)	:arrow_up:
src/tox/ToxAdapterFriendListener.vala	0% <0%> (ø)	:arrow_up:
src/db/SqliteSettingsDatabase.vala	0% <0%> (ø)	:arrow_up:
src/viewmodel/UserInfoViewModel.vala	0% <0%> (ø)	:arrow_up:
... and 28 more

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