Make E2E test suite configurable for non-localhost Armada server

[richscott]

ArmadaSparkE2E.scala, scripts/dev-e2e.sh, and conf/spark-defaults.conf assume the Armada server is always hosted on localhost, and runs the actual tests in a local Docker container.

The code should be adjusted so testing an armada-spark client that uses a remote Armada server host should be possible. The changes (so far) should be:

• make the constructor in ArmadaSparkE2E pass the Armada server's hostname to the ArmadaClient constructor

• scripts/dev-e2e.sh should use ARMADA_MASTER, etc for setting props passed

• conf/spark-defaults.conf should have its spark.armada.lookouturl configured dynamically

• the armada-operator repo should get a new (separate) kind-config.yaml that opens the Armada API and Lookout ports for external access

• Also, the scripts/set-version.sh script fails if running on macOS and sed is the Apple default version - the script should look for gsed and use that when running on macOS, otherwise use /usr/bin//sed.