translate IntSum to Sum in otlp_wrappers

[codeboten]

Description:
Deprecating IntSum As per https://github.com/open-telemetry/opentelemetry-proto/blob/f3b0ee0861d304f8f3126686ba9b01c106069cb0/opentelemetry/proto/metrics/v1/metrics.proto#L156, the OTLP receiver will translate IntSum into Sum.

Link to tracking Issue: Part of #3534

Testing: Added a test to ensure both Sum and IntSum are valid Sum after translation.

This change is built on top of #3619, will rebase once merged.

[bogdandrutu]

Tests failing:

=== RUN   TestSendMetrics
    otlp_test.go:295: 
        	Error Trace:	otlp_test.go:295
        	Error:      	Not equal: 
        	            	expected: pdata.Metrics{orig:(*v1.ExportMetricsServiceRequest)(0xc00000e380)}
        	            	actual  : pdata.Metrics{orig:(*v1.ExportMetricsServiceRequest)(0xc0003aa860)}
        	            	
        	            	Diff:
        	Test:       	TestSendMetrics

[bogdandrutu]

I think that is a good sign, it seems that the otlp receiver executes the code :)

[bogdandrutu]

Update comment?

[codeboten]

Updated!

[bogdandrutu]

Instead of adding new method maybe consider to change the other one and add same TODO.

[codeboten]

I thought adding another func would be less invasive, but it turns out I was wrong. Will add the same TODO to all the places I change here.

[codeboten]

@bogdandrutu I ended up adding 2 temporary test methods, changing the existing one caused all sorts of problems with other tests that were depending on them.

I plan on tackling the IntDataPoint/DoubleDataPoint conversion to NumberDataPoint soon, which will allow us to remove these temporary functions.

[bogdandrutu]

Please rebase