Move inspector_overlay to the top level

This CL moves inspector_overlay out of the front_end folder.
Unit tests remain under the front_end for now as we need to see
how to move them (they rely on karma config and helpers).

Design doc: https://docs.google.com/document/d/1yuQoNPtH2KxSFKoz3bRrQKu9wrPUjW4hx7idzAxb_B4/edit

Bug: 1100925
Change-Id: I0da88d9aae33602572d11485a3cbb46b5e3d588f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2395397
Reviewed-by: Mathias Bynens <[email protected]>
Reviewed-by: Tim van der Lippe <[email protected]>
Reviewed-by: Yang Guo <[email protected]>
Reviewed-by: Patrick Brosset <[email protected]>
Commit-Queue: Alex Rudenko <[email protected]>
diff --git a/BUILD.gn b/BUILD.gn
index 672ae19..8de4da6 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -291,7 +291,7 @@
 }
 
 group("generate_devtools_inspector_overlay_resources") {
-  public_deps = [ "front_end/inspector_overlay:build_inspector_overlay" ]
+  public_deps = [ "inspector_overlay:build_inspector_overlay" ]
 }
 
 copy("copy_emulated_devices_images") {