feat(TracerRegistry): set default name when nothing is provided

[mayurkale22]

Which problem is this PR solving?

• Resolves TracerRegistry: set name to default #679

/cc @dyladan @bg451

[codecov-io]

Codecov Report

Merging #681 into master will decrease coverage by 1.82%.
The diff coverage is 98.3%.

@@            Coverage Diff             @@
##           master     #681      +/-   ##
==========================================
- Coverage   91.58%   89.75%   -1.83%     
==========================================
  Files         217      214       -3     
  Lines       10156    10077      -79     
  Branches      916      936      +20     
==========================================
- Hits         9301     9045     -256     
- Misses        855     1032     +177

Impacted Files	Coverage Δ
...ry-tracing/test/export/ConsoleSpanExporter.test.ts	100% <ø> (ø)	⬆️
...ry-tracing/test/export/SimpleSpanProcessor.test.ts	100% <ø> (ø)	⬆️
...lemetry-plugin-http/test/functionals/utils.test.ts	99.35% <ø> (ø)	⬆️
packages/opentelemetry-web/test/WebTracer.test.ts	0% <ø> (ø)	⬆️
...entelemetry-exporter-zipkin/test/transform.test.ts	100% <ø> (ø)	⬆️
packages/opentelemetry-tracing/test/Span.test.ts	100% <ø> (ø)	⬆️
...try-tracing/test/export/BatchSpanProcessor.test.ts	100% <ø> (ø)	⬆️
...elemetry-plugin-dns/test/functionals/utils.test.ts	98.82% <ø> (ø)	⬆️
...opentelemetry-core/src/trace/globaltracer-utils.ts	81.81% <0%> (-18.19%)	⬇️
...ackages/opentelemetry-node/test/NodeTracer.test.ts	100% <100%> (ø)	⬆️
... and 55 more

[obecny]

lgtm

[OlivierAlbertini]

LGTM

[dyladan]

See my comment on the related issue. I don't see a technical problem here, but I don't think we should merge something like this without addressing that.

[dyladan]

Talked to spec about it today. The name property is definitely not optional. The reason the wording about having fallback behavior is in there is because some languages (javascript included) cannot strictly enforce that the api is called correctly.

[dyladan]

There was also consensus in the spec today that the name will be used to namespace the metrics at least in some cases but it was not decided. I'm happy moving forward with this for now, but know that it will likely change in the near future.

[mayurkale22]

@dyladan we should close this one, right?

[dyladan]

Probably. The history will be cleaner if we make an update to the examples to give them good names on their own PR.