Increase some of Gerrit's in-memory cache pools

We're seeing high system load and decreased performance on our
production Gerrit instance. Some research suggests this may be I/O
contention which can be relieved through better caching:

    https://groups.google.com/g/repo-discuss/c/7CemrH4lVJE

According to `gerrit show-caches --show-jvm --show-threads` some of
our memory-only caches are already at their default maximums after
only a few days of operation, and one in particular
(changeid_project) has a particularly poor cache hit ratio of 24% at
the moment. Increase changeid_project from the 1024 entry default by
32x (manual tests at 8x approached 50% cache hit), increase projects
by 4x (greater than the number of repos we host for now), and double
the others (groups_bysubgroup, permission_sort) since they still had
reasonable cache hit ratios while full. Also alpha-order the
existing cache overrides in our config for improved maintainability.

This will require a Gerrit service restart to take effect, once the
file update has been deployed.

Change-Id: Ieecd1802ce53cc0d37c68476b94b44cbe36fbd6e

playbooks/roles/gerrit/templates/gerrit.config

@@ -47,16 +47,24 @@
 	maxQueued = 200
 [cache]
 	directory = cache
-[cache "web_sessions"]
-	maxAge = 7days
 [cache "accounts"]
     memoryLimit = 32768
 [cache "accounts_byemail"]
     memoryLimit = 32768
 [cache "accounts_byname"]
     memoryLimit = 32768
+[cache "changeid_project"]
+    memoryLimit = 32768
+[cache "groups_bysubgroup"]
+    memoryLimit = 2048
 [cache "groups_byuuid"]
     memoryLimit = 32768
+[cache "permission_sort"]
+    memoryLimit = 2048
+[cache "projects"]
+    memoryLimit = 4096
+[cache "web_sessions"]
+	maxAge = 7days
 [user]
 	email = review@openstack.org
 [change]