[#24570] YSQL: Fix data race on MockClock's status

Summary:
### Issue

Test ClockSynchronizationTest.TestClockSkewError fails with tsan failure

```
WARNING: ThreadSanitizer: data race (pid=226462)
  Read of size 8 at 0x7b4000000bf0 by thread T82:
    #0 boost::intrusive_ptr<yb::Status::State>::get() const ${YB_THIRDPARTY_DIR}/installed/tsan/include/boost/smart_ptr/intrusive_ptr.hpp:181:16 (libyb_util.so+0x3c5994)
    #1 bool boost::operator==<yb::Status::State>(boost::intrusive_ptr<yb::Status::State> const&, std::nullptr_t) ${YB_THIRDPARTY_DIR}/installed/tsan/include/boost/smart_ptr/intrusive_ptr.hpp:263:14 (libyb_util.so+0x3c5994)
    #2 yb::Status::ok() const ${YB_SRC_ROOT}/src/yb/util/status.h:120:51 (libyb_util.so+0x3c5994)
    #3 yb::MockClock::Now() ${YB_SRC_ROOT}/src/yb/util/physical_time.cc:141:3 (libyb_util.so+0x3c5994)
    #4 yb::server::HybridClock::NowWithError(yb::HybridTime*, unsigned long*) ${YB_SRC_ROOT}/src/yb/server/hybrid_clock.cc:155:22 (libserver_common.so+0xa5e12)
    #5 yb::server::HybridClock::NowRange() ${YB_SRC_ROOT}/src/yb/server/hybrid_clock.cc:144:3 (libserver_common.so+0xa5ceb)
    #6 yb::ClockBase::Now() ${YB_SRC_ROOT}/src/yb/common/clock.h:26:29 (libtserver.so+0x23a77a)
    #7 yb::tserver::Heartbeater::Thread::TryHeartbeat() ${YB_SRC_ROOT}/src/yb/tserver/heartbeater.cc:437:41 (libtserver.so+0x23a77a)
    #8 yb::tserver::Heartbeater::Thread::DoHeartbeat() ${YB_SRC_ROOT}/src/yb/tserver/heartbeater.cc:650:19 (libtserver.so+0x23d05f)
    #9 yb::tserver::Heartbeater::Thread::RunThread() ${YB_SRC_ROOT}/src/yb/tserver/heartbeater.cc:697:16 (libtserver.so+0x23d74d)
    #10 decltype(*std::declval<yb::tserver::Heartbeater::Thread*&>().*std::declval<void (yb::tserver::Heartbeater::Thread::*&)()>()()) std::__invoke[abi:ue170006]<void (yb::tserver::Heartbeater::Thread::*&)(), yb::tserver::Heartbeater::Thread*&, void>(void (yb::tserver::Heartbeater::Thread::*&)(), yb::tserver::Heartbeater::Thread*&) ${YB_THIRDPARTY_DIR}/installed/tsan/libcxx/include/c++/v1/__type_traits/invoke.h:308:25 (libtserver.so+0x24206b)
...

  Previous write of size 8 at 0x7b4000000bf0 by main thread:
    #0 boost::intrusive_ptr<yb::Status::State>::swap(boost::intrusive_ptr<yb::Status::State>&) ${YB_THIRDPARTY_DIR}/installed/tsan/include/boost/smart_ptr/intrusive_ptr.hpp:210:16 (libyb_util.so+0x3c5c54)
    #1 boost::intrusive_ptr<yb::Status::State>::operator=(boost::intrusive_ptr<yb::Status::State>&&) ${YB_THIRDPARTY_DIR}/installed/tsan/include/boost/smart_ptr/intrusive_ptr.hpp:122:61 (libyb_util.so+0x3c5c54)
    #2 yb::Status::operator=(yb::Status&&) ${YB_SRC_ROOT}/src/yb/util/status.h:98:7 (libyb_util.so+0x3c5c54)
    #3 yb::MockClock::Set(yb::PhysicalTime const&) ${YB_SRC_ROOT}/src/yb/util/physical_time.cc:147:16 (libyb_util.so+0x3c5c54)
    #4 yb::ClockSynchronizationTest_TestClockSkewError_Test::TestBody() ${YB_SRC_ROOT}/src/yb/integration-tests/clock_synchronization-itest.cc:131:15 (clock_synchronization-itest+0x12e3ca)
    #5 void testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:2599:10 (libgtest.so.1.12.1+0x894f9)
    #6 void testing::internal::HandleExceptionsInMethodIfSupported<testing::Test, void>(testing::Test*, void (testing::Test::*)(), char const*) ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:2635:14 (libgtest.so.1.12.1+0x894f9)
    #7 testing::Test::Run() ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:2674:5 (libgtest.so.1.12.1+0x6123f)
    #8 testing::TestInfo::Run() ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:2853:11 (libgtest.so.1.12.1+0x62a05)
    #9 testing::TestSuite::Run() ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:3012:30 (libgtest.so.1.12.1+0x63f04)
    #10 testing::internal::UnitTestImpl::RunAllTests() ${YB_THIRDPARTY_DIR}/src/googletest-1.12.1/googletest/src/gtest.cc:5870:44 (libgtest.so.1.12.1+0x7be3d)
...

**SUMMARY**: ThreadSanitizer: data race ${YB_THIRDPARTY_DIR}/installed/tsan/include/boost/smart_ptr/intrusive_ptr.hpp:181:16 in boost::intrusive_ptr<yb::Status::State>::get() const
```

### Fix

Do what value_ does => wrap mock_status_ in boost::atomic.
Jira: DB-13604

Test Plan:
Jenkins

Ran

```
./yb_build.sh tsan --cxx-test integration-tests_clock_synchronization-itest --gtest_filter ClockSynchronizationTest.TestClockSkewError -n 50
```

Reviewers: asrivastava

Reviewed By: asrivastava

Subscribers: ybase

Differential Revision: https://phorge.dev.yugabyte.com/D39315

src/yb/util/physical_time.cc

@@ -138,16 +138,21 @@ const PhysicalClockPtr& AdjTimeClock() {
 #endif
 
 Result<PhysicalTime> MockClock::Now() {
-  RETURN_NOT_OK(mock_status_);
+  {
+    std::lock_guard status_lock(status_mutex_);
+    RETURN_NOT_OK(mock_status_);
+  }
   return CheckClockSyncError(value_.load(boost::memory_order_acquire));
 }
 
 void MockClock::Set(const PhysicalTime& value) {
   value_.store(value, boost::memory_order_release);
+  std::lock_guard status_lock(status_mutex_);
   mock_status_ = Status::OK();
 }
 
 void MockClock::Set(Status status) {
+  std::lock_guard status_lock(status_mutex_);
   mock_status_ = status;
 }
 

src/yb/util/physical_time.h

@@ -15,6 +15,7 @@
 
 #include <functional> // For std::function
 #include <memory>
+#include <mutex>
 
 #include <boost/atomic.hpp>
 
@@ -65,7 +66,8 @@ class MockClock : public PhysicalClock {
   // Set by calls to SetMockClockWallTimeForTests().
   // For testing purposes only.
   boost::atomic<PhysicalTime> value_{{0, 0}};
-  Status mock_status_;
+  Status mock_status_ GUARDED_BY(status_mutex_);
+  std::mutex status_mutex_;
 };
 
 const PhysicalClockPtr& WallClock();