Thread API cleanup

This patch cleans up the thread API and comes with the following
noteworthy changes:

- Introduced Cpu_session::Weight type that replaces a formerly used
  plain integer value to prevent the accidental mix-up of
  arguments.
- The enum definition of Cpu_session::DEFAULT_WEIGHT moved to
  Cpu_session::Weight::DEFAULT_WEIGHT
- New Thread constructor that takes a 'Env &' as first argument.
  The original constructors are now marked as deprecated. For the
  common use case where the default 'Weight' and 'Affinity' are
  used, a shortcut is provided. In the long term, those two
  constructors should be the only ones to remain.
- The former 'Thread<>' class template has been renamed to
  'Thread_deprecated'.
- The former 'Thread_base' class is now called 'Thread'.
- The new 'name()' accessor returns the thread's name as 'Name'
  object as centrally defined via 'Cpu_session::Name'. It is meant to
  replace the old-fashioned 'name' method that takes a buffer and size
  as arguments.
- Adaptation of the thread test to the new API

Issue #1954

repos/dde_bsd/src/lib/audio/scheduler.cc

@@ -60,7 +60,7 @@ bool Bsd::Task::run()
 	if (_state == STATE_INIT) {
 		/* setup execution environment and call task's function */
 		_state = STATE_RUNNING;
-		Genode::Thread_base *th = Genode::Thread_base::myself();
+		Genode::Thread *th = Genode::Thread::myself();
 
 		_stack = th->alloc_secondary_stack(_name, _stack_size);
 
@@ -107,7 +107,7 @@ Bsd::Task::Task(void (*func)(void*), void *arg, char const *name,
 Bsd::Task::~Task()
 {
 	if (_stack)
-		Genode::Thread_base::myself()->free_secondary_stack(_stack);
+		Genode::Thread::myself()->free_secondary_stack(_stack);
 }
 
 
@@ -191,7 +191,7 @@ void Bsd::Scheduler::schedule()
 #include <timer_session/connection.h>
 
 namespace {
-	struct Logger : Genode::Thread<0x4000>
+	struct Logger : Genode::Thread_deprecated<0x4000>
 	{
 		Timer::Connection  _timer;
 		Bsd::Scheduler     &_scheduler;
@@ -199,7 +199,7 @@ namespace {
 
 		Logger(Bsd::Scheduler &scheduler, unsigned interval_seconds)
 		:
-			Genode::Thread<0x4000>("logger"),
+			Genode::Thread_deprecated<0x4000>("logger"),
 			_scheduler(scheduler), _interval(interval_seconds)
 		{
 			start();