Migrate the Hub to React and make it deployable on-premises

As the previous attempt to update the Hub fell short (see #76), we're launching a new initiative with some new potential contributors. Following discussions during the spring, the goal is now clear: to transition the Hub to React technology. But before diving into technical details, let's remind some goals, requirements and constraints that will allow us to put some guardrails on the tasks to come:

1. The functional goal is to move the Hub UC to something friendly that can be easily customized (logo, name, colors, styles) for in-house/on-premises usage.
2. The technical goal is to migrate the existing old stack (mainly Angular 8 and Bootstrap 4) to an up-to-date React-based ecosystem,
3. As stated in the `DEPENDENCY_POLICY.md` file, we'd like to integrate 3rd party dependencies only when it makes sense (ie: the usage or diversity requirements are somewhat strong enough to justify pulling out a dependency). There's a strong requirement that picked dependencies must have compatible licensing terms with the CNCF policy.
4. Selected library, project structure, implementation code, and so on should be aligned with common standards and best practices within the field to make future maintenance easy and welcome many more contributions!
5. The produced Hub frontend should be easily embeddable as a web component (or a library if a web component is not possible) so that it will be seamlessly reused across other frontends like the Microcks application itself, a Microcks Backstage plugin, or any custom-made internal developer portal.

I know we have people out there ready for suggestions. Let's keep this issue opened as a global tracking point and let's deep dive into specific scoped task discussions via sub-issues.

Thanks!

Start by reviewing the prior attempt in issue #76 and the dependency constraints in DEPENDENCY_POLICY.md. This issue names no implementation entry point or tests, so use its sub-issues to define scoped migration and on-premises deployment tasks, along with their acceptance criteria.

Written by the indexing model from the issue text.