metric: rename from metrics

Generally use non-plural names.  Do a trivial rename of the Metric
definitions before they start being used by applications.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ia0f210684c8aa0f567d5a1d70baf7eb8956b8712
diff --git a/gen/xyz/openbmc_project/meson.build b/gen/xyz/openbmc_project/meson.build
index 573a389..b30b985 100644
--- a/gen/xyz/openbmc_project/meson.build
+++ b/gen/xyz/openbmc_project/meson.build
@@ -88,7 +88,7 @@
 subdir('Logging')
 subdir('MCTP')
 subdir('Memory')
-subdir('Metrics')
+subdir('Metric')
 subdir('Network')
 subdir('Nvme')
 subdir('Object')