[8.x](backport #6401) Split packaging into separate steps

[mergify]

What does this PR do?

Splitting centralized packaging step into separate steps to speed up builds.
Currently packagin takes up to 30 mins to run:

With thae changes in current PR packaging in total takes up to 15 mins:

Buildkite builds: https://buildkite.com/elastic/elastic-agent-extended-testing/builds?branch=split-packaging

NB! Failure of Win2022:sudo:upgrade test is not related to changes in current PR.

Why is it important?

Since the integration test steps are divided by platforms, we can divide packaging into the corresponding steps and run integration tests for the platform as soon as the required artifacts are built without waiting for the rest.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in ./changelog/fragments using the changelog tool
• I have added an integration test or an E2E test

Related issues

• Relates: https://github.com/elastic/ingest-dev/issues/4712

Questions to ask yourself

• How are we going to support this in production?
• How are we going to measure its adoption?
• How are we going to debug this?
• What are the metrics I should take care of?
• ...

---

This is an automatic backport of pull request #6401 done by [Mergify](https://mergify.com).

[mergify]

Cherry-pick of e956b4d has failed:

On branch mergify/bp/8.x/pr-6401
Your branch is up to date with 'origin/8.x'.

You are currently cherry-picking commit e956b4d2d.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   .buildkite/bk.integration.pipeline.yml
	modified:   .buildkite/integration.pipeline.yml

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   .buildkite/scripts/steps/integration-package.sh

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

[mergify]

This pull request has not been merged yet. Could you please review and merge it @oakrizan? 🙏

[elastic-sonarqube]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
No data about Coverage
No data about Duplication

See analysis details on SonarQube