GoLang docker image: actionloop-golang ==> action-golang

[dgrove-oss]

openwhisk-runtime-go PR#109 changed the name used to publish docker
images from actionloop-golang-VERSION to action-golang-VERSION. This
PR updates the core system runtime.json and documentation to use the
new names. All old images are still available on dockerhub and will
not be removed or renamed, so this should be a non-disruptive change.

[codecov-io]

Codecov Report

Merging #4674 into master will decrease coverage by 6.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4674      +/-   ##
==========================================
- Coverage   84.69%   78.58%   -6.12%     
==========================================
  Files         192      192              
  Lines        8686     8686              
  Branches      599      599              
==========================================
- Hits         7357     6826     -531     
- Misses       1329     1860     +531

Impacted Files	Coverage Δ
...core/database/cosmosdb/RxObservableImplicits.scala	0% <0%> (-100%)	⬇️
...ore/database/cosmosdb/cache/CacheInvalidator.scala	0% <0%> (-100%)	⬇️
...core/database/cosmosdb/CosmosDBArtifactStore.scala	0% <0%> (-96.17%)	⬇️
...tabase/cosmosdb/cache/CacheInvalidatorConfig.scala	0% <0%> (-94.74%)	⬇️
...sk/core/database/cosmosdb/CosmosDBViewMapper.scala	0% <0%> (-92.6%)	⬇️
...e/database/cosmosdb/cache/ChangeFeedListener.scala	0% <0%> (-86.67%)	⬇️
...e/database/cosmosdb/cache/KafkaEventProducer.scala	0% <0%> (-76.48%)	⬇️
...whisk/core/database/cosmosdb/CosmosDBSupport.scala	0% <0%> (-74.08%)	⬇️
...a/org/apache/openwhisk/common/ExecutorCloser.scala	0% <0%> (-66.67%)	⬇️
...abase/cosmosdb/CosmosDBArtifactStoreProvider.scala	7.69% <0%> (-50%)	⬇️
... and 12 more

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