Port the core package file feature from EE to CE
### Problem to solve If we want to support file upload for release API https://gitlab.com/gitlab-org/gitlab/issues/17838 in a way that will leverage all the work we did for workhorse object storage acceleration and the effort in https://gitlab.com/gitlab-org/gitlab-ce/issues/59232 we should consider porting the basic feature of ~"devops:package" to GitLab-core. ~"Maven Repository" and ~"NPM Registry" will not be ported, only the basic `Package` and `PackageFile` model. /cc @jlenny
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