Validate example config files with tests

This should ensure that all our examples (not just the ones we
generate config specs from) are up to date with the latest releases.

config_test.go

@@ -93,3 +93,30 @@ func TestHostname(t *testing.T) {
 		ReadBufferSizeBytes: defaultBufferSizeBytes,
 		OmitEmptyHostname:   true})
 }
+
+func TestVeneurExamples(t *testing.T) {
+	tests := []string{
+		"example.yaml",
+		"example_host.yaml",
+	}
+	for _, elt := range tests {
+		test := elt
+		t.Run(test, func(t *testing.T) {
+			t.Parallel()
+			_, err := ReadConfig(test)
+			assert.NoError(t, err)
+		})
+	}
+}
+
+func TestProxyExamples(t *testing.T) {
+	tests := []string{"example_proxy.yaml"}
+	for _, elt := range tests {
+		test := elt
+		t.Run(test, func(t *testing.T) {
+			t.Parallel()
+			_, err := ReadProxyConfig(test)
+			assert.NoError(t, err)
+		})
+	}
+}

example_host.yaml

@@ -1,12 +1,12 @@
 ---
-api_hostname: https://app.datadoghq.com
+datadog_api_hostname: https://app.datadoghq.com
+datadog_api_key: "farts"
 metric_max_length: 4096
 trace_max_length_bytes: 16384
 flush_max_per_body: 25000
 debug: true
 enable_profiling: true
 interval: "10s"
-key: "farts"
 # Numbers larger than 1 will enable the use of SO_REUSEPORT, make sure
 # this is supported on your platform!
 num_workers: 96
@@ -24,7 +24,8 @@ stats_address: "localhost:8125"
 tags:
  - "foo:bar"
  - "baz:quz"
-udp_address: "localhost:8126"
+statsd_listen_addresses:
+  - "udp://localhost:8126"
 #http_address: "einhorn@0"
 http_address: ""