Introduce replacement for getting and setting thread name: (#4312)

* In namespace ripple, introduces get_name function that takes a
  std:🧵:native_handle_type and returns a std::string.
* In namespace ripple, introduces get_name function that takes a
  std::thread or std::jthread and returns a std::string.
* In namespace ripple::this_thread, introduces get_name function
  that takes no parameters and returns the name of the current
  thread as a std::string.
* In namespace ripple::this_thread, introduces set_name function
  that takes a std::string_view and sets the name of the current
  thread.
* Intended to replace the beast utilities setCurrentThreadName
  and getCurrentThreadName.

src/ripple/app/main/LoadManager.cpp

@@ -21,8 +21,8 @@
 #include <ripple/app/main/LoadManager.h>
 #include <ripple/app/misc/LoadFeeTrack.h>
 #include <ripple/app/misc/NetworkOPs.h>
+#include <ripple/basics/ThreadUtilities.h>
 #include <ripple/basics/UptimeClock.h>
-#include <ripple/beast/core/CurrentThreadName.h>
 #include <ripple/json/to_string.h>
 #include <memory>
 #include <mutex>
@@ -99,7 +99,7 @@ LoadManager::stop()
 void
 LoadManager::run()
 {
-    beast::setCurrentThreadName("LoadManager");
+    this_thread::set_name("LoadManager");
 
     using namespace std::chrono_literals;
     using clock_type = std::chrono::steady_clock;