Expand network backups JSON blob into separate tables

[puddly]

This PR requires #1835 to be merged first, as otherwise there is too much churn during normal network operation.

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In order to fully backup and restore a Ziggurat network, we will need to persist a bit more data in the zigpy database. This PR breaks up the monolithic backup JSON into separate tables, allowing us to update counters, etc. without rewriting the whole JSON blob at once. It allows us to backup and restore active routes, child devices, etc. and quickly restart the stack.

[codecov]

Codecov Report

❌ Patch coverage is 95.49550% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.43%. Comparing base (925ea3d) to head (0b18aa4).

Files with missing lines	Patch %	Lines
zigpy/appdb.py	93.50%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #1856      +/-   ##
==========================================
- Coverage   99.47%   99.43%   -0.04%     
==========================================
  Files          57       57              
  Lines       12026    12121      +95     
==========================================
+ Hits        11963    12053      +90     
- Misses         63       68       +5     

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