Support invoke tree

[lgarithm]

For example-2 which outputs the following invoke summary

	summary of tracer_ctx_t::global (4.386451s)
--------------------------------------------------------------------------------
   count      cumulative (s)               %       mean (ms)    call site
--------------------------------------------------------------------------------
       1            4.386159           99.99       4386.1591    main
      43            4.385608           99.98        101.9909    work
       1            4.374317           99.72       4374.3174    h
       1            0.010054            0.23         10.0539    g
       1            0.001700            0.04          1.6999    f

it should output the invoke tree in addition

	invoke tree of tracer_ctx_t::global (4.386451s)
--------------------------------------------------------------------------------
   count      cumulative (s)               %       mean (ms)    call chain
--------------------------------------------------------------------------------
      43                                                        main
       1                                                           |-f
      20                                                           | |-work
       1                                                           |-g
      10                                                           | |-work
       1                                                           |-h
      13                                                             |-work

[lgarithm]

        invoke tree of stack_tracer_ctx_t_::global (3.978917s)
--------------------------------------------------------------------------------
   count      cumulative (s)               %       mean (ms)    call chain
--------------------------------------------------------------------------------
       1            3.978886          100.00       3978.8857    /0
       1            3.968196           99.73       3968.1963    /0/4
      13            3.968079           99.73        305.2368    /0/4/2
       1            0.010421            0.26         10.4211    /0/3
      10            0.010399            0.26          1.0399    /0/3/2
       1            0.000210            0.01          0.2100    /0/1
      20            0.000175            0.00          0.0088    /0/1/2

[lgarithm]

        invoke tree of stack_tracer_ctx_t_::global (4.004867s)
--------------------------------------------------------------------------------
   count      cumulative (s)               %       mean (ms)    call chain
--------------------------------------------------------------------------------
       1            4.004839          100.00       4004.8390    /main
       1            3.995336           99.76       3995.3364    /main/h
      13            3.995283           99.76        307.3295    /main/h/work
       1            0.009242            0.23          9.2418    /main/g
      10            0.009234            0.23          0.9234    /main/g/work
       1            0.000200            0.01          0.2003    /main/f
      20            0.000168            0.00          0.0084    /main/f/work