feat: validate metric names

[dyladan]

Which problem is this PR solving?

• Fixes Validate Metric names #465

Short description of the changes

• Ensure metric names are valid according to the spec
• Invalid metric names return noop implementations (per SIG meeting)

[codecov-io]

Codecov Report

Merging #468 into master will increase coverage by 0.36%.
The diff coverage is 95.16%.

@@            Coverage Diff            @@
##           master    #468      +/-   ##
=========================================
+ Coverage   94.83%   95.2%   +0.36%     
=========================================
  Files         130     125       -5     
  Lines        6524    6295     -229     
  Branches      556     519      -37     
=========================================
- Hits         6187    5993     -194     
+ Misses        337     302      -35

Impacted Files	Coverage Δ
packages/opentelemetry-metrics/test/Meter.test.ts	100% <100%> (ø)	⬆️
packages/opentelemetry-metrics/src/Meter.ts	80% <76.92%> (-5.72%)	⬇️
...ges/opentelemetry-exporter-zipkin/src/transform.ts	100% <0%> (ø)	⬆️
...telemetry-plugin-grpc/test/utils/assertionUtils.ts	100% <0%> (ø)	⬆️
.../opentelemetry-exporter-zipkin/test/zipkin.test.ts	100% <0%> (ø)	⬆️
...telemetry-scope-base/test/NoopScopeManager.test.ts	100% <0%> (ø)	⬆️
...entelemetry-exporter-zipkin/test/transform.test.ts	100% <0%> (ø)	⬆️
...es/opentelemetry-plugin-postgres/test/testUtils.ts
...entelemetry-plugin-postgres/test/assertionUtils.ts
... and 5 more

[mayurkale22]

Just curious, why do you need to use as - Type assertion here? Earlier it used to work, Is it because we are returning noop implementation?

[dyladan]

Yes, the function createCounter now returns types.Metric<types.CounterHandle> where it used to return just CounterMetric. The return type needed to be changed in order to allow returning the noop implementation which satisfies the type types.Metric<types.CounterHandle> but is not a CounterMetric

[mayurkale22]

Got you. As a user, I have to use/do the same assertion? This looks little inconvenient. WDYT?

[dyladan]

No you don't, because users will only use the public interface. This is only done because the tests access private fields