Parse newly added Snowflake statistics lines

[karsten]

As cohosh writes in #31157, Snowflake statistics files will soon ​contain new lines:

diff --git a/doc/broker-spec.txt b/doc/broker-spec.txt
index 2877784..eba3347 100644
--- a/doc/broker-spec.txt
+++ b/doc/broker-spec.txt
@@ -31,6 +31,24 @@ Metrics data from the Snowflake broker can be retrieved by sending an HTTP GET r
         A count of the total number of unique IP addresses of Snowflake
         proxies that have polled.
 
+    "snowflake-ips-standalone" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "standalone" that have polled.
+
+    "snowflake-ips-badge" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "badge" that have polled.
+
+    "snowflake-ips-webext" NUM NL
+        [At most once.]
+
+        A count of the total number of unique IP addresses of snowflake
+        proxies of type "webext" that have polled.
+
     "snowflake-idle-count" NUM NL
         [At most once.]

Let's parse these new lines in metrics-lib as soon as files containing them exist on CollecTor.

[karsten]

Please review ​commit 5fb36b7 in my task-32665 branch.

[irl]

lgtm

[karsten]

Thanks for looking! Merged to master. Closing.