Remove app_shell chrome.shell API and ShellAppWindow

The chrome.app.window API has been moved to src/extensions, so app_shell
no longer needs its custom chrome.shell API to open windows.

* Remove the API implementation -- mostly a manual revert of https://codereview.chromium.org/254473011/
* Remove app_shell_resources.grd since there are no more app_shell resources
* Remove athena's support for ShellAppWindow
* Fix example apps to remove the chrome.shell workaround.

No presubmit because it has a false-positive warning about the enum rename in extension_function_histogram_value.h

No try because no presubmit doesn't seem to work by itself.

BUG=413164
TEST=extensions_unittests, app_shell_unittests, app_shell_browsertests
[email protected] for deprecating an extension function histogram
NOPRESUBMIT=true
NOTRY=true

Review URL: https://codereview.chromium.org/571643003

Cr-Commit-Position: refs/heads/master@{#294852}
diff --git a/extensions/browser/extension_function_histogram_value.h b/extensions/browser/extension_function_histogram_value.h
index fc1ba2b7..3eaa577 100644
--- a/extensions/browser/extension_function_histogram_value.h
+++ b/extensions/browser/extension_function_histogram_value.h
@@ -807,7 +807,7 @@
   BLUETOOTHSOCKET_GETINFO,
   BLUETOOTHSOCKET_GETSOCKETS,
   WEBSTOREPRIVATE_SIGNINFUNCTION,
-  SHELL_CREATEWINDOW,
+  DELETED_SHELL_CREATEWINDOW,
   FILESYSTEMPROVIDERINTERNAL_GETMETADATAREQUESTEDSUCCESS,
   DELETED_FILESYSTEMPROVIDERINTERNAL_GETMETADATAREQUESTEDERROR,
   BROWSER_OPENTAB,