Rename the library as it includes more metrics than just usc

Summary: This diff renames the library in the `eden/facebook/metrics` directory from `usc` to `lib` as it includes more metrics than just usc. The changes made in the `fbcode/bento_kernels/eden/BUCK` file reflect this change by updating the dependency to `//eden/facebook/metrics:lib`.

Differential Revision: D72095290

fbshipit-source-id: fbd4acb1c1931f0e241a0099003ed7992b8a3244

Author: giorgidze

eden/facebook/metrics/BUCK

@@ -4,7 +4,7 @@ load("//bento:buck_macros.bzl", "bento_test_kernel")
 oncall("source_control")
 
 python_library(
-    name = "usc",
+    name = "lib",
     srcs = [
         "gk.py",
         "usc.py",