Tidy up KeyChain OWNERS

Tidy up the OWNERS file:
* Add all core team members.
* Add manager as emergency approver.
* Distinguish between emeritus and owners of related components.

Test: gerrit uploader
Bug: 33166666
Change-Id: I98ba2a56f677074fe0c35a2551ddab82be64da0b
diff --git a/OWNERS b/OWNERS
index 69f4e33..43172ed 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,5 +1,15 @@
-rgl@google.com
-jdanis@google.com
+# Core Enterprise security team
 eranm@google.com
+irinaid@google.com
+pgrafov@google.com
 rubinxu@google.com
+
+# Emergency
+sandness@google.com
+
+# KeyStore / Keymaster owners
+jdanis@google.com
 swillden@google.com
+
+# Emeritus owners
+rgl@google.com