test: pre-fill libstdc++ ctype caches before threads exist

- std::ctype<char> caches narrow()/widen() results per character in
  plain char arrays of the global classic-locale facet, written without
  synchronization from header-inlined code (locale_facets.h); two
  threads exercising an uncached character concurrently (e.g. compiling
  a std::regex in Channel::Validate) constitute a true data race that
  ThreadSanitizer rightfully reports
- the stores are real and unsynchronized, so a tsan-instrumented
  libstdc++ cannot help here; instead fill the caches before any thread
  is spawned, which turns every later access into a pure read
- warm the lazily-installed num_put/num_get caches used by stream
  insertion/extraction as well, via a small format/parse round-trip
- wire the warm-up into the gtest runner main() and, via a static
  initializer, into the test device runner

test/runner.cxx.in

@@ -10,6 +10,7 @@
 #include <TestEnvironment.h>
 
 #include <gtest/gtest.h>
+#include <helper/LocaleWarmup.h>
 
 #include <string>
 
@@ -24,6 +25,7 @@ string runTestDevice = "@RUN_TEST_DEVICE@";
 
 int main(int argc, char** argv)
 {
+    fair::mq::test::WarmUpLocaleCaches();
     ::testing::InitGoogleTest(&argc, argv);
     ::testing::FLAGS_gtest_death_test_style = "threadsafe";
     setenv("FAIRMQ_PATH", FAIRMQ_TEST_ENVIRONMENT, 0);