Implement OTLP Histogram

[leoparente]

Implemented based on Prometheus and guides provided by OpenTelemetry

Histograms
A Prometheus Histogram MUST be converted to an OTLP Histogram. Multiple Prometheus histogram metrics MUST be merged together into a single OTLP Histogram:
1, The le label on non-suffixed metrics is used to identify and order histogram bucket boundaries. Each Prometheus line produces one bucket count on the resulting histogram. Each value for the le label except +Inf produces one bucket boundary.
2, Lines with _count and _sum suffixes are used to determine the histogram’s count and sum.
3, If _count is not present, the metric MUST be dropped.
4, If _sum is not present, the histogram’s sum MUST be unset.

[leoparente]

Tested with exporter

Metric #5
Descriptor:
     -> Name: netprobe_response_histogram_us
     -> Description: Net Probe histogram in microseconds
     -> Unit: 
     -> DataType: Histogram
     -> AggregationTemporality: Unspecified
HistogramDataPoints #0
Data point attributes:
     -> handler: Str(default2-default_netprobe-net)
     -> policy: Str(default2)
     -> tap: Str(default_netprobe)
     -> target: Str(outlook)
StartTimestamp: 2023-01-10 20:42:12.399318495 +0000 UTC
Timestamp: 1970-01-01 00:00:00 +0000 UTC
Count: 1923
ExplicitBounds #0: 100000.000000
ExplicitBounds #1: 113646.000000
Buckets #0, Count: 1339
Buckets #1, Count: 1923