[docs] Add example tracing infrastructure (#1866)

This adds an example on how to get Grafana Tempo up to receive spans as
well as Grafana itself to view them.

I've added this as a separate Tracing doc in the installation guide as
the Advanced one was starting to get rather full.

Fixes: #1791

example/tracing/tempo.yaml

@@ -0,0 +1,23 @@
+server:
+  http_listen_port: 3200
+
+distributor:
+  receivers:
+    otlp:
+      protocols:
+        grpc:
+
+ingester:
+  max_block_duration: 5m
+
+compactor:
+  compaction:
+    block_retention: 1h
+
+storage:
+  trace:
+    backend: local
+    wal:
+      path: /tmp/tempo/wal
+    local:
+      path: /tmp/tempo/blocks