[Fleet] Migrate installPackageByUpload and installCustomPackage to state machine and clean up

[criamico]

Closes #189346
Closes #189347

Summary

Final PR for part I of package lifecycle improvements.

• Migrate both installPackageByUpload and installCustomPackage to installPackageWithStateMachine and clean up the old code. As the state machine is been working in production for two releases, I am confident in using it for the custom and upload packages without a feature flag.

Testing

• Try installing a custom package
• Try installing a package via upload

They should work as usual

Checklist

• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios

[obltmachine]

🤖 GitHub comments

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Just comment with:

• /oblt-deploy : Deploy a Kibana instance using the Observability test environments.
• run docs-build : Re-trigger the docs validation. (use unformatted text in the comment!)

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[kibana-ci]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: f2681cf

Failed CI Steps

• FTR Configs #93

Test Failures

• [job] [logs] FTR Configs #93 / Rules Management - Prebuilt Rules - Large Prebuilt Rules Package @ess @serverless @skipInServerlessMKI install_large_prebuilt_rules_package should install a package containing 15000 prebuilt rules without crashing

Metrics [docs]

✅ unchanged

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

cc @criamico