Add support for starting debugged application without waiting for a debugger to attach

[nkvoll]

In an automated workflow, I'm building multiple images and deploying them to K8s. I would still like to be able to attach a debugger.

However, this currently surfaces some problems:

1. Every time I rebuild, I need to attach a debugger for the deploy to complete successfully. Since I often deploy more than one container, the number of debuggers I need to restart may be >1, and this becomes cumbersome to juggle locally.
2. If I don't need breakpoints to be set for initialization / start-up code, requiring a debugger attachment before starting just slows down deployment/start-up/iteration time.

Delve supports a --continue flag, which lets the application start without waiting, and I can (optionally) connect a debugger at any later point in the lifecycle. This PR exposes this via a --debug-continue flag. I was considering adding some more general --delve-opts="--continue ..." flag, but I wasn't sure whether that would be worth the effort / desirable, so I opted for this simpler approach. Let me know what you think :)

[github-actions]

This Pull Request is stale because it has been open for 90 days with
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[nkvoll]

I still think this is relevant, and I don't have FOSSA access to check what the licence compliance issues would be all about - I don't expect any licensing to be changed by this PR.