Release 4.0 tracker

[lresende]

Using this issue to track the must haves before we can start cutting a 4.0 release

• [x] https://github.com/elyra-ai/elyra/pull/3201
• [x] https://github.com/elyra-ai/elyra/pull/3145
• [x] https://github.com/elyra-ai/elyra/pull/3258
• [x] https://github.com/elyra-ai/elyra/pull/3256
• [x] https://github.com/elyra-ai/elyra/pull/3167
• [x] https://github.com/elyra-ai/elyra/pull/3160
• [x] https://github.com/elyra-ai/elyra/pull/3141

[caponetto]

@lresende I believe it'd be nice to have the PRs below (from ODH) cherry-picked for the release. The first one is an improvement to build the release artifacts (frontend) using the production scripts, and the other two are bug fixes. I can send a PR for each one of them. Please let me know if I can proceed.

EDIT: Cherry-picks:

ODH Elyra	Elyra
#50	https://github.com/elyra-ai/elyra/pull/3269
#87	https://github.com/elyra-ai/elyra/pull/3271
#88	https://github.com/elyra-ai/elyra/pull/3270

[lresende]

@caponetto I tried to cherry-pick some of these with conflicts or other issues. Maybe it would be easier if you submitted a PR with some details on how to validate. We might also need to update some docs for the dev/prod builds.

[caponetto]

@lresende I have submitted the PRs. Please take a look at them when you have some time.

[lresende]

We should be ready for release after the rc5 released today.

[lresende]

https://github.com/elyra-ai/elyra/releases/tag/v4.0.0

[hadesto]

congrats on the new release!!