Unify the pattern of using a package-level logger (#8245)

Co-authored-by: Preston Van Loon <preston@prysmaticlabs.com>

validator/web/BUILD.bazel

@@ -8,6 +8,7 @@ go_library(
     srcs = [
         "doc.go",
         "handler.go",
+        "log.go",
         ":site_data",  # keep
     ],
     importpath = "github.com/prysmaticlabs/prysm/validator/web",

validator/web/handler.go

@@ -5,16 +5,10 @@ import (
 	"net/http"
 	"net/url"
 	"path"
-
-	"github.com/sirupsen/logrus"
 )
 
 const prefix = "external/prysm_web_ui/prysm-web-ui"
 
-var (
-	log = logrus.WithField("prefix", "prysm-web")
-)
-
 // Handler serves web requests from the bundled site data.
 var Handler = func(res http.ResponseWriter, req *http.Request) {
 	u, err := url.ParseRequestURI(req.RequestURI)

validator/web/log.go

@@ -0,0 +1,5 @@
+package web
+
+import "github.com/sirupsen/logrus"
+
+var log = logrus.WithField("prefix", "prysm-web")