[flytepropeller] Add Tests in v1alpha.go including `array_test.go`, `branch_test.go`, `error_test.go`, and `iface_test.go` with 0.13% Coverage Improvment #580

Job	Run time
unpack-envvars	1s
Docker Build Images (flyteadmin) / build_docker	5m 1s
Docker Build Images (datacatalog) / build_docker	2m 56s
Docker Build Images (flytecopilot) / build_docker	2m 28s
Docker Build Images (flytepropeller) / build_docker	5m 58s
Build Images / Build & Push Image (flyteadmin) / Push to Github Registry	3m 53s
Build Images / Build & Push Image (datacatalog) / Push to Github Registry	3m 38s
Build Images / Build & Push Image (flytecopilot) / Push to Github Registry	2m 41s
Build Images / Build & Push Image (flytepropeller) / Push to Github Registry	6m 41s
Build Images / Build & Push Image (flytescheduler) / Push to Github Registry	6m 53s
Check Go Generate (flytecopilot) / Go Generate	1m 31s
Check Go Generate (datacatalog) / Go Generate	1m 24s
Check Go Generate (flyteadmin) / Go Generate	3m 43s
Unit Tests (datacatalog) / Run Unit Test	3m 49s
Unit Tests (flyteadmin) / Run Unit Test	7m 21s
Check Go Generate (flytepropeller) / Go Generate	2m 42s
Unit Tests (flytecopilot) / Run Unit Test	3m 27s
Lint (datacatalog) / Run Lint	2m 13s
Lint (flyteadmin) / Run Lint	5m 20s
Lint (flyteidl) / Run Lint	2m 33s
Unit Tests (flyteplugins) / Run Unit Test	6m 20s
Unit Tests (flytepropeller) / Run Unit Test	7m 19s
Unit Tests (flytestdlib) / Run Unit Test	4m 5s
Lint (flyteplugins) / Run Lint	3m 19s
Lint (flytepropeller) / Run Lint	6m 38s
Lint (flytestdlib) / Run Lint	2m 1s
Integration Test (flyteadmin) / Integration tests	8m 4s
	1h 51m 59s

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