[log] Make :vlog_is_on/:absl_vlog_is_on public in BUILD.bazel

No longer include vlog_is_on.h from log.h.  This is a breaking change.
To use VLOG_IS_ON(), absl/log/vlog_is_on.h must be included, not log.h.

PiperOrigin-RevId: 616045708
Change-Id: I59261eb5c28846557b43b040e187ec3ef36e4132

absl/log/BUILD.bazel

@@ -243,9 +243,6 @@ cc_library(
     hdrs = ["absl_vlog_is_on.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl/log:__subpackages__",
-    ],
     deps = [
         "//absl/base:config",
         "//absl/base:core_headers",
@@ -259,9 +256,6 @@ cc_library(
     hdrs = ["vlog_is_on.h"],
     copts = ABSL_DEFAULT_COPTS,
     linkopts = ABSL_DEFAULT_LINKOPTS,
-    visibility = [
-        "//absl/log:__subpackages__",
-    ],
     deps = [
         ":absl_vlog_is_on",
     ],

absl/log/log.h

@@ -198,7 +198,6 @@
 #define ABSL_LOG_LOG_H_
 
 #include "absl/log/internal/log_impl.h"
-#include "absl/log/vlog_is_on.h"  // IWYU pragma: export
 
 // LOG()
 //