Fix Select tool's scale nudging with multi-layer selection

[elbertronnie]

• Fix scale nudging for multiple selection in Select Tool as specified in https://discord.com/channels/731730685944922173/881073965047636018/1216986976670978129
• Use message discriminant for DEBUG_MESSAGE_BLOCK_LIST where possible as specified in https://github.com/GraphiteEditor/Graphite/pull/1690#discussion_r1527107297
• Remove unnecessary parameter from selected_bounds_document_space
• Fix the error: target.closest is not a function. It can be reproduced by:
  • Click on Help on the Menu bar
  • Hover over the option Debug: Print Messages
  • Watch the JS console