fix: fixes to devworkspace generator release

[mkuznyetsov]

What does this PR do?

Clear up inconsistencies, that occured during 7.74.0 release related to DevWorkspace Generator:

• dev branch project version suffix switched from 'snapshot' to 'next', for better consistency with other projects
• workflow that does npm publish will now be triggered for 7.x.y branches.
• this way, generator will be published as npm project under following tags:
  • "next" tag for main branch builds,
  • "7.x.y-next" for 7.x.y branch builds,
  • "7.x.y" & "latest" for the actual release version

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What issues does this PR fix or reference?

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PR Checklist

As the author of this Pull Request I made sure that:

• The Eclipse Contributor Agreement is valid
• Code produced is complete
• Code builds without errors
• Tests are covering the bugfix
• The repository devfile is up to date and works
• Sections What issues does this PR fix or reference and How to test this PR completed
• Relevant user documentation updated
• Relevant contributing documentation updated
• CI/CD changes implemented, documented and communicated

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[svor]

LGTM