Refactor the Prometheus remote write exporter to use OTLP v0.5.0

[huyan0]

This PR removes dependency on dataold and the old v0.4.0 OTLP definitions. It refactors code for metric conversion to convert from OTLP v0.5.0.

Changes in this PR includes:

• Replace references:
  • dataold.MetricsData -> data.MetricsData
  • pdatautil.OldInternal -> pdatautil.Internal
  • testdataold -> testdata (prefix was changed GenerateMetricData -> GenerateMetrics)
• Change helper methods to take in a pointer to a metric rather than a metric descriptor
• Create helper methods to get the type string from the metric
• Create helper methods for IntDataPoint, DoubleDataPoint, IntHistogramDataPoint , and DoubleHistogramDataPoint
• Replace OTLPv0.4.0 metrics with v0.5.0 metrics as inputs for unit tests. This accounted for a lot of the changes

Linked Issue: resolves #1681
Related PR: #1643

cc: @bogdandrutu @jmacd @alolita @huyan0

[codecov]

Codecov Report

Merging #1708 into master will decrease coverage by 0.07%.
The diff coverage is 99.40%.

@@            Coverage Diff             @@
##           master    #1708      +/-   ##
==========================================
- Coverage   92.39%   92.32%   -0.08%     
==========================================
  Files         264      264              
  Lines       19960    20049      +89     
==========================================
+ Hits        18442    18510      +68     
- Misses       1089     1110      +21     
  Partials      429      429              

Impacted Files	Coverage Δ
exporter/prometheusremotewriteexporter/helper.go	99.02% <99.21%> (-0.98%)	⬇️
exporter/prometheusremotewriteexporter/exporter.go	92.80% <100.00%> (-3.15%)	⬇️
internal/dataold/testdataold/metric.go	80.56% <0.00%> (-3.06%)	⬇️
consumer/pdatautil/pdatautil.go	84.09% <0.00%> (-2.28%)	⬇️

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