Improve error message for invalid .gitpod.yml configurations ("continue with default" options)

[loujaybee]

When you submit an invalid configuration to Gitpod, the error message, and the recovery mode are not entirely obvious. There have been cases where users have missed, or not understood the purpose of the "continue with default configuration" button, for instance seeking to go back to the last known working commit rather than trying to open in a recover mode that ignores the currently broken configuration. We should look to declutter this view, making:

1. It clearer that an error has occurred, exactly why, and the action to be taken (see screenshots).
2. The call to action (CTA) more obvious, "continue with default configuration" is not very clear.
3. Removing other visual noise that distracts the user from the CTA.

Note, I'm not providing specific wording or designs here, different designs and wording would have to be tested + explored.

Error message for incorrect gitpod.yml	Error message for failed workspace image build

[stale]

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