Nested config, devices registry

* All config now nested.
    - Use default config from model field default values. If providers
      should be enabled by default, non-empty default config file could
      be provided again.
    - Environment variable support with EOS_ prefix and __ between levels,
      e.g. EOS_SERVER__EOS_SERVER_PORT=8503 where all values are case
      insensitive.
      For more information see:
      https://docs.pydantic.dev/latest/concepts/pydantic_settings/#parsing-environment-variable-values
    - Use devices as registry for configured devices. DeviceBase as base
      class with for now just initializion support (in the future expand
      to operations during optimization).
    - Strip down ConfigEOS to the only configuration instance. Reload
      from file or reset to defaults is possible.

 * Fix multi-initialization of derived SingletonMixin classes.

tests/test_measurement.py

@@ -3,7 +3,11 @@ import pytest
 from pendulum import datetime, duration
 
 from akkudoktoreos.config.config import SettingsEOS
-from akkudoktoreos.measurement.measurement import MeasurementDataRecord, get_measurement
+from akkudoktoreos.measurement.measurement import (
+    MeasurementCommonSettings,
+    MeasurementDataRecord,
+    get_measurement,
+)
 
 
 @pytest.fixture
@@ -186,8 +190,10 @@ def test_load_total_no_data(measurement_eos):
 def test_name_to_key(measurement_eos):
     """Test name_to_key functionality."""
     settings = SettingsEOS(
-        measurement_load0_name="Household",
-        measurement_load1_name="Heat Pump",
+        measurement=MeasurementCommonSettings(
+            measurement_load0_name="Household",
+            measurement_load1_name="Heat Pump",
+        )
     )
     measurement_eos.config.merge_settings(settings)
 
@@ -199,8 +205,10 @@ def test_name_to_key(measurement_eos):
 def test_name_to_key_invalid_topic(measurement_eos):
     """Test name_to_key with an invalid topic."""
     settings = SettingsEOS(
-        measurement_load0_name="Household",
-        measurement_load1_name="Heat Pump",
+        MeasurementCommonSettings(
+            measurement_load0_name="Household",
+            measurement_load1_name="Heat Pump",
+        )
     )
     measurement_eos.config.merge_settings(settings)