assert: refactor to avoid unsafe array iteration

[aduh95]

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines

[aduh95]

These changes come with some perf regressions:

 confidence improvement accuracy (*) (**) (***)
assert/ok.js n=100000 *** -6.77 % ±3.69% ±4.92% ±6.44%
assert/throws.js method='doesNotThrow' n=10000 *** -14.90 % ±5.67% ±7.56% ±9.86%

This may or may not be considered an acceptable trade-off.

[aduh95]

#37005 should help solve the perf issue.

EDIT: Nope, it doesn't help.

[BridgeAR]

I amgoing to close this due to the regressions and we didn't follow up anyway