Cache uri generation in json

[thorbjoernl]

Change Summary

Adds persistent caching of URIs to the jsonfiledb implementation, which speeds up iterating over uris significantly (once they have been cached).

INFO:aerovaldb.jsondb.jsonfiledb:Initializing aerovaldb for './tests/test-db/json' with locking False
json_files: 47 items in 0.117 seconds
sqlite:     47 items in 0.001 seconds
INFO:aerovaldb.jsondb.jsonfiledb:Initializing aerovaldb for './tests/test-db/json' with locking False
json_files: 47 items in 0.004 seconds (Cached)

Related issue number

#74

Checklist

• Start with a draft-PR
• The PR title is a good summary of the changes
• PR is set to AeroTools and a tentative milestone
• Documentation reflects the changes where applicable
• Tests for the changes exist where applicable
• Tests pass locally
• Tests pass on CI
• At least 1 reviewer is selected
• Make PR ready to review