crash: Add "crash-user-access" group.

This group will allow us to make the user's home crash directory
accessible to the user, `crash` (for the crash root reduction), and
`vm_cicerone` (so that we can collect crashes from within the VM).

BUG=chromium:1029076,chromium:782243
TEST=tast run --extrauseflags chrome_internal dut \
   ui.ChromeCrashLoggedIn.*
TEST=chgrp -R crash-user-access /home/chronos/crash/
TEST=(as crash) verify membership with `id`
TEST=(as crash) ls -al /home/chronos/crash/

Cq-Depend: chromium:1940837,chromium:1940812
Change-Id: Iac2c91c9a2b1c491d0168a71ae46c68cf08f2195
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/eclass-overlay/+/1940851
Tested-by: Miriam Zimmerman <mutexlox@chromium.org>
Commit-Queue: Miriam Zimmerman <mutexlox@chromium.org>
Reviewed-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Ian Barkley-Yeung <iby@chromium.org>
diff --git a/profiles/base/accounts/group/crash-user-access b/profiles/base/accounts/group/crash-user-access
new file mode 100644
index 0000000..8fdb623
--- /dev/null
+++ b/profiles/base/accounts/group/crash-user-access
@@ -0,0 +1,3 @@
+group:crash-user-access
+gid:420
+users:crash,chronos,vm_cicerone