Actually fix scrolling: the interactive_test_runner selector was broken

The reason for https://github.com/google/trace-viewer/commit/9d2402 was that
test scrolling was broken. This was reverted because the fix changed the actual
body to scroll.

The real bug was that the interactive-test-runner had lost its styling due
to a typo during the tvcm move. This caused it to not get sized,
which prevented it from overflowing, which prevented scrolling.

This fixes the styling, and everything works again.
InputLatencyTest was adding an event listener on the document, leading to flake.

Every test that ran after that point that caused a requestSelectionChanged
event would then fail.
Fix side_panel_container_test after registry refactoring
Make update_gyp_and_gn work when run relatively
Move trace_model*.html into trace_model/
cc.html -> cc/cc.html
Move cc/ to extras
Move tcmalloc and collapse/expand images to tcmalloc/
Move tcmalloc to extras
Move net to extras
move gpu to extras
Move system_stats to extras
Normalize importer/ folder so importer directories contain all aspects of the importer
Move importers to extras
Move side panels to extras
Show better message when an import fails to load
Move examples/trace_viewer dropdown to leftControls