Many improvements to die interpretations given our explorations into high_pc

[fosterbrereton]

• Adding documentation as we learn more about die attributes and values
• Adding use of adobe contract checks where assert needs to happen in release builds, too
• Adding number to attribute_value when the caller doesn't care what form the value takes on disk, and all valid values could be represented by either form.
• Improved handling of forms loclistx and rnglistx (which are starting to show in DWARF5 object files)
• Correct handling of implicit_const in a debug abbreviation (which is new to DWARF5)
• Better handling of DW_AT_inline
• Better handling of DW_AT_declaration
• Better handling of DW_AT_specification
• Improved die skipping logic when we are confident a die cannot contribute to ODRVs.
• Improved behaviors in orc_test, especially around running the rest of a test battery when one test fails.