tracing: Rename `eval_map_wq` and allow other parts of tracing use it

tracing: Rename `eval_map_wq` and allow other parts of tracing use it

The eval_map_work_func() function, though queued in eval_map_wq,
holds the trace_event_sem read-write lock for a long time during
kernel boot. This causes blocking issues for other functions.

Rename eval_map_wq to trace_init_wq and make it global, thereby
allowing other parts of tracing to schedule work on this queue
asynchronously and avoiding blockage of the main boot thread.

Link: https://patch.msgid.link/20260204015344.162818-1-tianyaxiong@kylinos.cn
Suggested-by: Steven Rostedt <rostedt@goodmis.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Yaxiong Tian <tianyaxiong@kylinos.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>