Add option to change the data type (from int to float or vice-versa)

[james-bebbington]

Link to tracking Issue: #332

Description:
Added an extension to the metric transform processor to allow changing the data type between int & float

[codecov]

Codecov Report

Merging #402 into master will increase coverage by 20.89%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           master     #402       +/-   ##
===========================================
+ Coverage   63.22%   84.11%   +20.89%     
===========================================
  Files          16      181      +165     
  Lines         677     9699     +9022     
===========================================
+ Hits          428     8158     +7730     
- Misses        225     1208      +983     
- Partials       24      333      +309     

Flag	Coverage Δ
#integration	63.22% <ø> (ø)
#unit	83.91% <100.00%> (?)

Impacted Files	Coverage Δ
...stransformprocessor/metrics_transform_processor.go	100.00% <100.00%> (ø)
exporter/sapmexporter/exporter.go	88.88% <0.00%> (ø)
...orter/signalfxexporter/metricdata_to_signalfxv2.go	88.57% <0.00%> (ø)
exporter/newrelicexporter/factory.go	68.42% <0.00%> (ø)
exporter/elasticexporter/factory.go	83.33% <0.00%> (ø)
receiver/signalfxreceiver/factory.go	94.11% <0.00%> (ø)
exporter/awsxrayexporter/factory.go	100.00% <0.00%> (ø)
exporter/splunkhecexporter/metricdata_to_splunk.go	74.48% <0.00%> (ø)
...eiver/k8sclusterreceiver/collection/replicasets.go	0.00% <0.00%> (ø)
...xporter/alibabacloudlogserviceexporter/uploader.go	100.00% <0.00%> (ø)
... and 161 more

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