timers: attach listOnTimeout function to TimerWrap

This avoid continuous deoptimizations cycles in V8 for the listOnTimeout function by attaching it to the TimeWrap prototype. It improves insertion and cancellation time of unpooled timers by 18% and 28% respectively.

$ cat timewrap.csv | Rscript benchmark/compare.R
                                                    improvement confidence      p.value
 timers/immediate.js type="breadth" thousands=5000      -1.23 %            6.471883e-01
 timers/immediate.js type="breadth1" thousands=5000      6.23 %          * 4.589025e-02
 timers/immediate.js type="breadth4" thousands=5000     -0.28 %            8.716988e-01
 timers/immediate.js type="clear" thousands=5000         1.61 %            2.157496e-01
 timers/immediate.js type="depth" thousands=5000         0.68 %            2.223863e-01
 timers/immediate.js type="depth1" thousands=5000       -0.26 %            7.391597e-01
 timers/set-immediate-breadth-args.js millions=5        -1.31 %            4.186285e-01
 timers/set-immediate-breadth.js millions=10             3.01 %            2.234333e-01
 timers/set-immediate-depth-args.js millions=5           0.92 %            6.154973e-01
 timers/timers-breadth.js thousands=5000                 1.78 %            4.422721e-01
 timers/timers-cancel-pooled.js millions=5               0.78 %            5.467502e-01
 timers/timers-cancel-unpooled.js millions=1            27.60 %        *** 1.806596e-59
 timers/timers-depth.js thousands=1                      0.32 %            5.568216e-01
 timers/timers-insert-pooled.js millions=5               0.47 %            7.908426e-01
 timers/timers-insert-unpooled.js millions=1            18.19 %        *** 4.666303e-46
 timers/timers-timeout-pooled.js millions=10            -0.69 %            4.534725e-01

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Affected core subsystem(s)

timers