Merge pull request atom#5858 from atom/as-faster-fold-destroy

Speed up `destroyFoldsIntersectingBufferRange`

Remove isInitialEmptyEditor

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Merge pull request atom#5733 from as-cii/efficient-cursor-merging

🐎 Speed up `mergeCursors`

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Fix race when starting atom twice in spec

Restore old behavior of atom.open

Use ATOM_HOME env var in protocol handler

Closes atom#5501

Update cursors as soon as all required measurements are assigned