Key Value re-*factor*ing

[rylev]

Similar in scope to #2840. This is just a refactoring and so only impacts users of the key-value factor library.

• Removes the idea of a "default" store manager instead relying on runtime config handling to add a store manager for the default label.
• The "default" store manager is now added directly after runtime config is deserialized from toml.
• The key-value factor tests are reimagined
  • The tests now try to verify the actual behavior of the factor and not of the runtime config
  • Runtime configuration is now tested in the runtime config crate.

[lann]

OOO FANCY