[dashboard] Redirect to /blocked when trying to create or start a workspace while blocked

[jankeromnes]

Fixes #3783

[jankeromnes]

How to test:

• Log in with GitHub OAuth at https://jx-redirect-blocked.staging.gitpod-dev.com/login
• Open a GitLab workspace, e.g. https://jx-redirect-blocked.staging.gitpod-dev.com/#https://gitlab.com/gitpod/spring-petclinic -- the GitLab OAuth redirect should be fast / barely noticeable (note: you may see a GitLab login/confirmation screen, or nothing GitLab-related if you had already authorized dev-staging before, but the redirect itself should be fast)
• Stop that workspace again from https://jx-redirect-blocked.staging.gitpod-dev.com/workspaces
• Next, open this PR in Gitpod: https://gitpod.io/#https://github.com/gitpod-io/gitpod/pull/3785
• Run kubectl port-forward deployments/mysql 3306 & and then mysql -h 127.0.0.1 -p (password is test)
• Run use gitpod and then select id, name, blocked from d_b_user; -- this will show your user ID
• Run update d_b_user set blocked = 1 where id = '<ID>'; (where <ID> is your own user ID)
• Going back to https://jx-redirect-blocked.staging.gitpod-dev.com/workspaces, try to restart your old workspace, or to create a new workspace

In both cases, you should get quickly redirected to /blocked:

[jankeromnes]

@gtsiolis or @AlexTugarev, please take a look if you have time 😊 (Priority: 🔅 Low)

[AlexTugarev]

redirect on blocked state worked!

[AlexTugarev]

Works nicely! 🙏