PixelRadDamDigitization: Fix runtime error "No factory found"

This MR addresses a bugfix to fix a runtime error present since rel 21.0.98

In the first version m_EfieldInterpolator was not intialized properly, from commit 646dc2c5 (comment 2745088) on changed but causes runtime error.

Now an instance of the tool with default configuration will be retrieved as a private tool.

Tagging @jchapman, @bnachman , @mbomben , @stsuno who were involved in the discussion.