tracing: Move saved_cmdline code into trace_sched_switch.c

The code that handles saved_cmdlines is split between the trace.c file and
the trace_sched_switch.c. There's some history to this. The
trace_sched_switch.c was originally created to handle the sched_switch
tracer that was deprecated due to sched_switch trace event making it
obsolete. But that file did not get deleted as it had some code to help
with saved_cmdlines. But trace.c has grown tremendously since then. Just
move all the saved_cmdlines code into trace_sched_switch.c as that's the
only reason that file still exists, and trace.c has gotten too big.

No functional changes.

Link: https://lore.kernel.org/linux-trace-kernel/20240220140703.497966629@goodmis.org

Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Vincent Donnefort <vdonnefort@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Mete Durlu <meted@linux.ibm.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

kernel/trace/trace.h

@@ -1375,6 +1375,16 @@ static inline void trace_buffer_unlock_commit(struct trace_array *tr,
 	trace_buffer_unlock_commit_regs(tr, buffer, event, trace_ctx, NULL);
 }
 
+DECLARE_PER_CPU(bool, trace_taskinfo_save);
+int trace_save_cmdline(struct task_struct *tsk);
+int trace_create_savedcmd(void);
+int trace_alloc_tgid_map(void);
+void trace_free_saved_cmdlines_buffer(void);
+
+extern const struct file_operations tracing_saved_cmdlines_fops;
+extern const struct file_operations tracing_saved_tgids_fops;
+extern const struct file_operations tracing_saved_cmdlines_size_fops;
+
 DECLARE_PER_CPU(struct ring_buffer_event *, trace_buffered_event);
 DECLARE_PER_CPU(int, trace_buffered_event_cnt);
 void trace_buffered_event_disable(void);