Calculate sample rate correctly

[simonswine]

The flamebearer metadata passes the sample rate to the frontend:

pyroscope/pkg/og/structs/flamebearer/flamebearer.go

Line 85 in 9bc2847

SampleRate uint32 `json:"sampleRate"`

, we currently hard code the value:

pyroscope/pkg/model/flamegraph.go

Line 128 in 9bc2847

sampleRate := uint32(100)

While the older version of flamebearer calculated it from PeriodDuration:

pyroscope/pkg/og/structs/flamebearer/convert/convert.go

Lines 199 to 204 in 9bc2847

	if c, ok := tree.DefaultSampleTypeMapping[stype]; ok {
	units = c.Units
	if c.Sampled && p.Period > 0 {
	sampleRate = uint32(time.Second / time.Duration(p.Period))
	}
	}

In reality the data in Duration is not propagated correctly in our query path as those values remain unpopulated.

#4192

Related #3342