feat(sdk-metrics)!: export factory functions over classes

[pichlermarc]

Currently types of private properties end up being part of the public interface, which causes breaking changes left, right and center. Using a factory function we can only expose what we want the user to use, this enables us to make larger changes to SDK internals without breaking users.

Note: This is combined with #4931 as it also eliminates some classes that we previously exported.

Old:

const { MeterProvider, PeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics');
const { OTLPMetricExporter } =  require('@opentelemetry/exporter-metrics-otlp-proto');

const meterProvider = new MeterProvider({
  readers: [
    new PeriodicExportingMetricReader({
      exporter: new OTLPMetricExporter(),
      exportIntervalMillis: 1000,
    })
  ]
});

New:

const { createMeterProvider, createPeriodicExportingMetricReader } = require('@opentelemetry/sdk-metrics');
const { OTLPMetricExporter } =  require('@opentelemetry/exporter-metrics-otlp-proto');

const meterProvider = createMeterProvider({
  readers: [ 
    createPeriodicExportingMetricReader({
      exporter: new OTLPMetricExporter(),
      exportIntervalMillis: 1000,
    })
  ]
});

For a user it's actually a fairly minimal change but for us it means that we can freely modify the SDK's MeterProvider and all previously unintentionally public referenced and transitively referenced types.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.25%. Comparing base (b057c93) to head (a762455).
Report is 3 commits behind head on next.

Additional details and impacted files

@@           Coverage Diff           @@
##             next    #4932   +/-   ##
=======================================
  Coverage   93.24%   93.25%           
=======================================
  Files         318      318           
  Lines        8231     8239    +8     
  Branches     1651     1651           
=======================================
+ Hits         7675     7683    +8     
  Misses        556      556           

Files with missing lines	Coverage Δ
...imental/packages/opentelemetry-sdk-node/src/sdk.ts	95.48% <100.00%> (ø)
...es/shim-opencensus/src/OpenCensusMetricProducer.ts	100.00% <ø> (ø)
packages/sdk-metrics/src/MeterProvider.ts	100.00% <100.00%> (ø)
...es/sdk-metrics/src/export/ConsoleMetricExporter.ts	84.61% <100.00%> (+1.28%)	⬆️
...s/sdk-metrics/src/export/InMemoryMetricExporter.ts	92.00% <100.00%> (+0.69%)	⬆️
...etrics/src/export/PeriodicExportingMetricReader.ts	93.22% <100.00%> (+0.23%)	⬆️
packages/sdk-metrics/src/view/View.ts	100.00% <ø> (ø)

[trentm]

Looking good.

Here are some more hits of the old usage in docs and examples to apply to your branch:
https://gist.github.com/trentm/889d78ad727c53aae1e10244768cd9a6

[pichlermarc]

Here are some more hits of the old usage in docs and examples to apply to your branch: https://gist.github.com/trentm/889d78ad727c53aae1e10244768cd9a6

Thanks for pointing that out - there were actually a few more things that needed changing from the previous PRs I made for that package, I applied them all in e2a36a9 and a762455