* add computed backend vars
* finish computed backend vars, add tests
* fix token for AppHarness with redis state manager
* fix timing issues
* add unit tests for computed backend vars
* automagically mark cvs with _ prefix as backend var
* fully migrate backend computed vars
* rename is_backend_variable to is_backend_base_variable
* add integration test for implicit backend cv, adjust comments
* replace expensive backend var check at runtime
* keep stuff together
* simplify backend var check method, consistent naming, improve test typing
* fix: do not convert properties to cvs
* add test for property
* fix cached_properties with _ prefix in state cls
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