Move unit tests for (PD)CHECK into a separate file

This is in preparation for moving these macros out of logging.h

Bug: 1031540
Change-Id: I29aa4ce07dcb7b165b72a6fa4b8dda4f8371e4c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2139152
Auto-Submit: Hans Wennborg <hans@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Hans Wennborg <hans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#757001}

base/BUILD.gn

@@ -2493,6 +2493,7 @@ test("base_unittests") {
     "callback_list_unittest.cc",
     "callback_unittest.cc",
     "cancelable_callback_unittest.cc",
+    "check_unittest.cc",
     "command_line_unittest.cc",
     "component_export_unittest.cc",
     "containers/adapters_unittest.cc",