refactor(test): prefer forEach instead of map

[ferhatelmas]

Which problem is this PR solving?

• prefer forEach over map unless the generated array is needed.

Short description of the changes

• makes the intention clearer.

[codecov-io]

Codecov Report

Merging #556 into master will decrease coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #556      +/-   ##
=========================================
- Coverage   90.22%   90.2%   -0.02%     
=========================================
  Files         150     150              
  Lines        7435    7462      +27     
  Branches      663     669       +6     
=========================================
+ Hits         6708    6731      +23     
- Misses        727     731       +4

Impacted Files	Coverage Δ
packages/opentelemetry-tracing/test/Span.test.ts	100% <ø> (ø)	⬆️
...ckages/opentelemetry-plugin-grpc/test/grpc.test.ts	96.11% <100%> (ø)	⬆️
...-scope-zone-peer-dep/test/ZoneScopeManager.test.ts	0% <0%> (ø)	⬆️
...s/opentelemetry-core/test/trace/NoopTracer.test.ts	60% <0%> (ø)	⬆️
...lemetry-core/test/trace/ProbabilitySampler.test.ts	56.52% <0%> (ø)	⬆️
...elemetry-core/test/trace/spancontext-utils.test.ts	55.55% <0%> (ø)	⬆️
...s/opentelemetry-core/test/context/B3Format.test.ts	63.39% <0%> (ø)	⬆️
...ges/opentelemetry-core/test/trace/NoopSpan.test.ts	63.63% <0%> (ø)	⬆️
...s/opentelemetry-core/test/trace/tracestate.test.ts	65.06% <0%> (ø)	⬆️
...pentelemetry-core/test/internal/validators.test.ts	50% <0%> (ø)	⬆️
... and 64 more

[dyladan]

In general do we prefer Array.prototype.forEach or for..of syntax? I prefer for..of usually.

[mayurkale22]

https://medium.com/@abustamam/for-loops-vs-foreach-in-javascript-7a977278a39e

[draffensperger]

One interesting note is that for (const of loops can sometimes optimize better with the Closure compiler (useful for certain web builds) since it enables it to do better reachability analysis of the code. I also like it for style reasons, but I'm open to .forEach.

[draffensperger]

Definitely prefer forEach to map when the eventual list is not used

[obecny]

lgtm