Remove internal formula helper types from the public interface

This is about the `FormulaEnginePool` and `ResampledFormulaBuilder`
which became public when `formula_engine` became a public module in
the previous commit.

Signed-off-by: Sahas Subramanian <[email protected]>

Author: shsms

src/frequenz/sdk/timeseries/battery_pool/_battery_pool_reference_store.py

@@ -17,7 +17,7 @@
 from ...actor.power_distributing._battery_pool_status import BatteryStatus
 from ...microgrid import connection_manager
 from ...microgrid.component import ComponentCategory
-from ..formula_engine import FormulaEnginePool
+from ..formula_engine._formula_engine_pool import FormulaEnginePool
 from ._methods import MetricAggregator
 
 

src/frequenz/sdk/timeseries/ev_charger_pool/_ev_charger_pool.py

@@ -20,7 +20,8 @@
 from ...microgrid.component import ComponentCategory, ComponentMetricId
 from .. import Sample, Sample3Phase
 from .._quantities import Current, Power, Quantity
-from ..formula_engine import FormulaEngine, FormulaEngine3Phase, FormulaEnginePool
+from ..formula_engine import FormulaEngine, FormulaEngine3Phase
+from ..formula_engine._formula_engine_pool import FormulaEnginePool
 from ..formula_engine._formula_generators import (
     EVChargerCurrentFormula,
     EVChargerPowerFormula,

src/frequenz/sdk/timeseries/formula_engine/__init__.py

@@ -4,12 +4,8 @@
 """A formula engine for applying formulas."""
 
 from ._formula_engine import FormulaEngine, FormulaEngine3Phase
-from ._formula_engine_pool import FormulaEnginePool
-from ._resampled_formula_builder import ResampledFormulaBuilder
 
 __all__ = [
     "FormulaEngine",
     "FormulaEngine3Phase",
-    "FormulaEnginePool",
-    "ResampledFormulaBuilder",
 ]

src/frequenz/sdk/timeseries/logical_meter/_logical_meter.py

@@ -11,7 +11,8 @@
 from ...actor import ChannelRegistry, ComponentMetricRequest
 from ...microgrid.component import ComponentMetricId
 from .._quantities import Current, Power, Quantity
-from ..formula_engine import FormulaEngine, FormulaEngine3Phase, FormulaEnginePool
+from ..formula_engine import FormulaEngine, FormulaEngine3Phase
+from ..formula_engine._formula_engine_pool import FormulaEnginePool
 from ..formula_engine._formula_generators import (
     CHPPowerFormula,
     ConsumerPowerFormula,

tests/timeseries/_formula_engine/utils.py

@@ -13,7 +13,9 @@
 from frequenz.sdk.microgrid.component import ComponentMetricId
 from frequenz.sdk.timeseries import Sample
 from frequenz.sdk.timeseries._quantities import QuantityT
-from frequenz.sdk.timeseries.formula_engine import ResampledFormulaBuilder
+from frequenz.sdk.timeseries.formula_engine._resampled_formula_builder import (
+    ResampledFormulaBuilder,
+)
 
 
 def get_resampled_stream(