main-refactor-Identifier

Start of refactor, building on tests introduced:

• Remove use of preprocessor type definition in Identifier header
• Move static_assert into testing code
• Remove redundant .cxx file with default d'tor for IdHelper
• Move RangeParser from class to free functions in new namespace
• Update RangeParser to use charconv (incomplete, needs more tests)
• Otherwise cosmetic:remove redundant comments