ComponentAccumulator configuration for SCT digitization

Define new style replacements for PixelDigitizationConfig.py.

ToolSetup dependencies also converted to new style.

ConfigFlags initialisation set up for Digitization and Overlay, with legacy keys inserted.

Also makes minor updates to BCM_Digitization.

Add ConditionsStore StoreGateSvc in tests.

Tests for all new modules.

This duplicates most of !21340 (closed), but without Pixel digitization which has ongoing issues.