Dismantle AbstractInstrumentBuilder inheritance hierarchy

[breedx-splk]

Replaces #5772.

The use of inheritance for code reuse via AbstractInstrumentBuilder was a bitter pill to swallow. I think this cleans up considerably with some delegation and improved encapsulation.

I don't believe that this changes any public facing APIs.

I think that all of the Sdk{MetricType}Builder classes are just pure delegation now.

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Files	Coverage Δ
...o/opentelemetry/sdk/metrics/InstrumentBuilder.java	100.00% <100.00%> (ø)
...io/opentelemetry/sdk/metrics/SdkDoubleCounter.java	96.77% <92.30%> (-3.23%)	⬇️
...a/io/opentelemetry/sdk/metrics/SdkDoubleGauge.java	95.23% <90.00%> (-4.77%)	⬇️
.../opentelemetry/sdk/metrics/SdkDoubleHistogram.java	96.55% <90.00%> (-3.45%)	⬇️
...ntelemetry/sdk/metrics/SdkDoubleUpDownCounter.java	96.00% <92.30%> (-4.00%)	⬇️
...a/io/opentelemetry/sdk/metrics/SdkLongCounter.java	96.55% <90.90%> (-3.45%)	⬇️
...ava/io/opentelemetry/sdk/metrics/SdkLongGauge.java	95.65% <92.30%> (-4.35%)	⬇️
...io/opentelemetry/sdk/metrics/SdkLongHistogram.java	96.96% <91.66%> (-3.04%)	⬇️
...pentelemetry/sdk/metrics/SdkLongUpDownCounter.java	95.65% <90.90%> (-4.35%)	⬇️

... and 6 files with indirect coverage changes

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[mateuszrzeszutek]

Missing tests for all of these?

[breedx-splk]

Are you suggesting that we should have tests for toString() methods?

[mateuszrzeszutek]

We do for some (most?) of the toString() methods; perhaps we should add them for the instrument builders as well.

[breedx-splk]

Hmmm, I've traditionally been hesitant to test toString() because it's supposed to be purely informative and relying on toString() for real programmatic concerns is probably a bad, fragile practice.

In this case, I might also shy away from testing it because the implementation relies on the toString() of several other classes, including autovalue generated toString() from the InstrumentDescriptor. Is that really that helpful?

[jack-berg]

Sorry for not getting to this sooner. It's been low priority for me since its just a refactor. But if you're willing to pick it back up I will respond promptly and work to get this approved / merged 🙂.