Meta: Sync State & Storage for v0.15

[Dominik1999]

Sync State & Storage for v0.15

Tracking issue for sync state and storage improvements in the v0.15 release.

Issues

• Improvements on sync state #1759 - Improvements on sync state (PR refactor: sync state #1995)
• Follow-up improvements on consumed notes tracking #1978 - Follow-up improvements on consumed notes tracking
• InputNoteReader cannot find notes consumed externally #1971 - InputNoteReader cannot find notes consumed externally
• Prune MMR authentication nodes alongside blocks #2001 - Prune MMR authentication nodes alongside blocks
• Store decryption keys in the client #1613 - Store decryption keys in the client
• Store account keys securely #30 - Store account keys securely (v0.14 spillover)