[DH-301] new deployment workflow for edx, fix minor typo in base deployer workflow

[shaneknapp]

since edx is running in a different cluster than the rest of the hubs, we need to authenticate to that cluster using GKE_KEY_EDX when setting up google-github-actions/setup-gcloud@v2.

i would prefer to not have two workflows for hub deployment, but i can't think of an elegant way to do this in deploy-hubs.yaml.

output of script when ignoring edx:

(dh) ➜  datahub git:(workflow-for-edx-deployment) ✗ # this will trigger all hubs to be deployed: GITHUB_PR_LABEL_HUB_IMAGES=1
(dh) ➜  datahub git:(workflow-for-edx-deployment) ✗ # how we currently deploy the hubs that have been ported to the new CI/CD
(dh) ➜  datahub git:(workflow-for-edx-deployment) ✗ GITHUB_PR_LABEL_HUB_IMAGES=1 .github/scripts/determine-hub-deployments.py --ignore edx --only-deploy gradebook logodev shiny stat159 stat20 nature a11y ugr01 data101 astro biology cee dev publichealth eecs julia data102 ischool
a11y
astro
biology
cee
data101
data102
dev
eecs
gradebook
ischool
julia
logodev
nature
publichealth
shiny
stat159
stat20
ugr01
(dh) ➜  datahub git:(workflow-for-edx-deployment) ✗ # and if we only want to deploy edx even if the env var declares "deploy them all"!
(dh) ➜  datahub git:(workflow-for-edx-deployment) ✗ GITHUB_PR_LABEL_HUB_IMAGES=1 .github/scripts/determine-hub-deployments.py --only-deploy edx
edx