[Fleet] Migrate installPackageByUpload and installCustomPackage to st…

…ate machine and clean up (#192438)

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](https://www.elastic.co/guide/en/kibana/master/development-documentation.html)
was added for features that require explanation or tutorials
- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios