Fix flaky lru_cache test

[cdce8p]

Proposed change

Sometimes test_override_single_value would fail during a CI run.

FAILED tests/helpers/test_entity_values.py::test_override_single_value - assert 3 == 1
 +  where 3 = CacheInfo(hits=0, misses=3, maxsize=16384, currsize=3).currsize
 +    where CacheInfo(hits=0, misses=3, maxsize=16384, currsize=3) = <built-in method cache_info of functools._lru_cache_wrapper object at 0x7f5e05ba78a0>()
 +      where <built-in method cache_info of functools._lru_cache_wrapper object at 0x7f5e05ba78a0> = <bound method EntityValues.get of <homeassistant.helpers.entity_values.EntityValues object at 0x7f5dc8f43da0>>.cache_info
 +        where <bound method EntityValues.get of <homeassistant.helpers.entity_values.EntityValues object at 0x7f5dc8f43da0>> = <homeassistant.helpers.entity_values.EntityValues object at 0x7f5dc8f43da0>.get

That is caused if test_override_by_domain and / or test_override_by_glob is run beforehand.
The reason is that the lru_cache is created for the class, not a specific entity. I.e.

store = EV(...)
store.get(val)

store2 = EV(...)
store2.get(val)

would create two cache entries even if val is the same.

--
To reproduce the error locally

pytest \
  tests/helpers/test_entity_values.py::test_override_by_domain \
  tests/helpers/test_entity_values.py::test_override_by_glob \
  tests/helpers/test_entity_values.py::test_override_single_value

Type of change

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[frenck]

Thanks, @cdce8p 👍

../Frenck