receiver/prometheus: roundtrip Prometheus->Pdata direct conversion without OpenCensus

[odeke-em]

Wire up and use the direct Prometheus->Pdata conversion end to end.
With this change the receiver will no longer need OpenCensus.

This change will involve more follow-ups that just migrate over the tests,
because we don't want a super bloated/massive PR.

Fixes #3691
Depends on PR #3694
Depends on PR #3695

[linux-foundation-easycla]

The committers are authorized under a signed CLA.

• ✅ Emmanuel T Odeke (4b3c2be, c54089d, de99984, a847925, 5d85d10)

[tigrannajaryan]

Please rebase and fix conflicts.

[bogdandrutu]

ok  	go.opentelemetry.io/collector/receiver/otlpreceiver/internal/trace	0.058s
panic: interface conversion: v1.isMetric_Data is *v1.Metric_Sum, not *v1.Metric_Summary

goroutine 156 [running]:
go.opentelemetry.io/collector/model/pdata.Metric.Summary(...)
	D:/a/opentelemetry-collector/opentelemetry-collector/model/pdata/metrics.go:207
go.opentelemetry.io/collector/receiver/prometheusreceiver/internal.adjustStartTimestampPdata(0x40790ccccccccccd, 0xc000929708)
	D:/a/opentelemetry-collector/opentelemetry-collector/receiver/prometheusreceiver/internal/otlp_transaction.go:206 +0x1f0
go.opentelemetry.io/collector/receiver/prometheusreceiver/internal.(*transactionPdata).Commit(0xc0006328c0, 0x66fecc, 0xed89d97fb)
	D:/a/opentelemetry-collector/opentelemetry-collector/receiver/prometheusreceiver/internal/otlp_transaction.go:178 +0x1c5
github.com/prometheus/prometheus/scrape.(*scrapeLoop).scrapeAndReport.func1(0xc00001dce8, 0xc00001dcf8, 0xc00077f440)
	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1195 +0x50
github.com/prometheus/prometheus/scrape.(*scrapeLoop).scrapeAndReport(0xc00077f440, 0x3b9aca00, 0x3b9aca00, 0x0, 0x0, 0x0, 0x66fecc, 0xed89d97fb, 0x400bca0, 0x0, ...)
	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1262 +0xb58
github.com/prometheus/prometheus/scrape.(*scrapeLoop).run(0xc00077f440, 0x3b9aca00, 0x3b9aca00, 0x0)
	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1148 +0x37e
created by github.com/prometheus/prometheus/scrape.(*scrapePool).sync
	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:564 +0xa0e

[odeke-em]

ok  	go.opentelemetry.io/collector/receiver/otlpreceiver/internal/trace	0.058s

panic: interface conversion: v1.isMetric_Data is *v1.Metric_Sum, not *v1.Metric_Summary



goroutine 156 [running]:

go.opentelemetry.io/collector/model/pdata.Metric.Summary(...)

	D:/a/opentelemetry-collector/opentelemetry-collector/model/pdata/metrics.go:207

go.opentelemetry.io/collector/receiver/prometheusreceiver/internal.adjustStartTimestampPdata(0x40790ccccccccccd, 0xc000929708)

	D:/a/opentelemetry-collector/opentelemetry-collector/receiver/prometheusreceiver/internal/otlp_transaction.go:206 +0x1f0

go.opentelemetry.io/collector/receiver/prometheusreceiver/internal.(*transactionPdata).Commit(0xc0006328c0, 0x66fecc, 0xed89d97fb)

	D:/a/opentelemetry-collector/opentelemetry-collector/receiver/prometheusreceiver/internal/otlp_transaction.go:178 +0x1c5

github.com/prometheus/prometheus/scrape.(*scrapeLoop).scrapeAndReport.func1(0xc00001dce8, 0xc00001dcf8, 0xc00077f440)

	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1195 +0x50

github.com/prometheus/prometheus/scrape.(*scrapeLoop).scrapeAndReport(0xc00077f440, 0x3b9aca00, 0x3b9aca00, 0x0, 0x0, 0x0, 0x66fecc, 0xed89d97fb, 0x400bca0, 0x0, ...)

	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1262 +0xb58

github.com/prometheus/prometheus/scrape.(*scrapeLoop).run(0xc00077f440, 0x3b9aca00, 0x3b9aca00, 0x0)

	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:1148 +0x37e

created by github.com/prometheus/prometheus/scrape.(*scrapePool).sync

	C:/Users/runneradmin/go/pkg/mod/github.com/prometheus/prometheus@v1.8.2-0.20210621150501-ff58416a0b02/scrape/scrape.go:564 +0xa0e

Thanks @bogdandrutu! Indeed, I should perhaps mark this PR as a draft because I have to translate the entire test suite, it's basically consumed most of my time for the past week. I'll actually mail small parts of it progressively.

[github-actions]

This PR was marked stale due to lack of activity. It will be closed in 7 days.

[bogdandrutu]

@odeke-em unfortunately this needs to be moved to contrib. Sorry and thanks :)