Move to keymanager/keymanageropts command line parameters (#4590)

* Move to keymanager/keymanageropts command line parameters

* Add help for individual keymanagers

* gazelle

Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>

validator/keymanager/BUILD.bazel

@@ -9,6 +9,7 @@ go_library(
         "direct_unencrypted.go",
         "keymanager.go",
         "log.go",
+        "opts.go",
     ],
     importpath = "github.com/prysmaticlabs/prysm/validator/keymanager",
     visibility = ["//validator:__subpackages__"],
@@ -27,6 +28,7 @@ go_test(
     srcs = [
         "direct_interop_test.go",
         "direct_test.go",
+        "opts_test.go",
     ],
     embed = [":go_default_library"],
     deps = [