Add Logging for Summary Datapoint to Logging Exporter

[JasonXZLiu]

Description:
This issue adds logging for the summary datapoint in the logging exporter. This is primarily added for testing purposes.

Link to tracking Issue: #1638

Resulting Logs

Metric #38
Descriptor:
     -> Name: rpc_durations_seconds
     -> Description: RPC latency distributions.
     -> Unit: s
     -> DataType: DoubleSummary
SummaryDataPoints #0
Data point labels:
     -> Namespace: rpc-app
     -> Service: rpc-app-service
     -> app: rpc-app
     -> container_name: rpc-app-cont
     -> service: exponential
StartTime: 1604691204093000000
Timestamp: 1604691234093000000
Count: 410
Sum: 0.000414
QuantileValue #0: Quantile 0.500000, Value 0.000001
QuantileValue #1: Quantile 0.900000, Value 0.000002
QuantileValue #2: Quantile 0.990000, Value 0.000005

[codecov]

Codecov Report

Merging #2084 (a7eceda) into master (6c8a896) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #2084      +/-   ##
==========================================
- Coverage   92.10%   92.09%   -0.01%     
==========================================
  Files         278      278              
  Lines       16977    16992      +15     
==========================================
+ Hits        15636    15649      +13     
- Misses        922      923       +1     
- Partials      419      420       +1     

Impacted Files	Coverage Δ
exporter/loggingexporter/logging_exporter.go	90.44% <100.00%> (+0.47%)	⬆️
translator/internaldata/resource_to_oc.go	88.73% <0.00%> (-2.82%)	⬇️

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[bogdandrutu]

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