Added --default-image option to be used with --shell-executor-no-image=false

[NGPetrov]

Currently if --shell-executor-no-image=false is used the runner defaults to docker.io/ruby:3.1.
In case isolation is required, there is no option to run the ci in a custom image.

Added --default-image option.
If set when --shell-executor-no-image=false, the value will be used as a image source for the container.
If not set when --shell-executor-no-image=false, the default docker.io/ruby:3.1 will be used.
If set when --shell-executor-no-image=true (or not set), warring message is displayed.
If set when --shell-isolation, warring message is displayed.

Fixed typo (or old option name) in arvg.ts:49, from --no-shell-executor-no-image to --shell-executor-no-image

Included 3 tests to validate proper runner image/shell is used.

[NGPetrov]

All fixes are implemented.
With a force push to keep the history clean.

[firecow]

What are these weird changes?

[NGPetrov]

The first version used had the parameter resolve to sting | null and the later check for argument clash was working fine.
After modifying the argument signature to get defaultImage() : string {, the argument clash check failed, as it treated the defaultImage as being always set.
I didn't thought it would be ok to remove the argument clash checks.
So I added another get to know, if the user explicitly set the default image, and so to check for incompatible arguments.

The need to modify it somehow was due to couple of tests failing.
The multiple force push-es due to my mistakes to push everything at once properly.

[firecow]

I'm talking about the specific no-op changes to package.json and package-lock.json 😄

[NGPetrov]

"...due to my mistakes to push everything at once properly"
Sorry about that, a bit of distractions and I completely pushed (multiple times) the wrong changes.

Now all of it is removed.
There are no unnecessary changes to package*.json or the files produces from tests.