Use staging Devfile registry for PR tests (#7129)

* Revert using a DEVFILE_PROXY env var

There is no proxy deployed in the internal test cluster.
As such, this env var no longer makes sense.

* To help troubleshoot, display the resolved Devfile registry URL

* Make interactive tests more resilient with stack versions

They are now able to determine if the "Select version" prompt
should be asked by "odo init" or not:

* Make sure doc automation tests do not rely on hard-coded namespaces

* Allow to run doc automation tests with more parallel Ginkgo nodes

This is possible now that those tests no longer
depend on a single hard-coded namespace.

* Remove occurrences of the DEVFILE_REGISTRY env var in IBM Pipelines scripts

* Reuse logic for determining the Devfile Registry URL in "odo registry" tests

* Clarify what openshiftci-config.sh is used for

pkg/config/config.go

@@ -8,7 +8,6 @@ import (
 )
 
 type Configuration struct {
-	DevfileProxy                  *string       `env:"DEVFILE_PROXY,noinit"`
 	DockerCmd                     string        `env:"DOCKER_CMD,default=docker"`
 	Globalodoconfig               *string       `env:"GLOBALODOCONFIG,noinit"`
 	OdoDebugTelemetryFile         *string       `env:"ODO_DEBUG_TELEMETRY_FILE,noinit"`

pkg/config/config_test.go

@@ -18,7 +18,6 @@ func TestDefaultValues(t *testing.T) {
 	checkDefaultBoolValue(t, "OdoExperimentalMode", cfg.OdoExperimentalMode, false)
 
 	// Use noinit to set non initialized value as nil instead of zero-value
-	checkNilString(t, "DevfileProxy", cfg.DevfileProxy)
 	checkNilString(t, "Globalodoconfig", cfg.Globalodoconfig)
 	checkNilString(t, "Globalodoconfig", cfg.Globalodoconfig)
 	checkNilString(t, "OdoDebugTelemetryFile", cfg.OdoDebugTelemetryFile)