[gjs] (10 commits) ...Merge branch 'atoms-refactor' into 'master'

[Philip Chimento <pchimento src gnome org>]

Summary of changes:

  1abdf08... context: Move all private context methods to C++ class
  d3994ff... context: Remove __gjsKeepAlive atom
  8e70774... context: Move atoms to a separate class
  5d5f82d... atoms: Use more atoms to avoid converting strings
  5c1a24a... atoms: Allow "symbol atoms" for keys not exposed to JS
  ac94032... importer: Remove special case for __iterator__
  74693df... js: Compare jsid in some resolve hooks instead of strings
  ebe8e11... atoms: use structs with operator()() override to init atoms
  9b40242... atoms: Make init functions fallible
  775d439... Merge branch 'atoms-refactor' into 'master'