dumpstate: Emit cgroup configuration

This file contains:
* A list of all controllers
* The version for each controller
* Whether each controller is enabled or not
* The total number of cgroups for each controller

Bug: 406851260
Test: adb bugreport br.zip # Check inside for /proc/cgroups contents
Flag: NONE Fails gracefully even if file doesn't exist / can't be accessed
Change-Id: I0dce60b73db4d0b366e71892e0c0f1bb1fcc4ca0

Author: tweej

cmds/dumpstate/dumpstate.cpp

@@ -1928,7 +1928,7 @@ Dumpstate::RunStatus Dumpstate::dumpstate() {
     // Add linker configuration directory
     ds.AddDir(LINKERCONFIG_DIR, true);
 
-    /* Dump frozen cgroupfs */
+    DumpFile("Cgroups", "/proc/cgroups");
     dump_frozen_cgroupfs();
 
     if (ds.dump_pool_) {