rt_backtrace_formatted_print() and rt_backtrace_to_buffer() to help
debug routines.

Also, following modification are included:
- make rt_backtrace_frame patchable with weak attr
- replace lwp backtrace with sync output

Signed-off-by: Shell <smokewood@qq.com>

marked this pull request as ready for review

polarvid changed the title [feat] Enhance support for backtrace service [kservice] Enhance support for backtrace service