Introduce a tree structure into the components and bases subdirectories

[marksto]

Is your feature request related to a problem? Please describe.
Having the workspace components (and maybe bases) semantically grouped in some way, e.g. by purpose, by layer, etc.

Describe the solution you'd like
Introduce a tree structure into the components and bases subdirectories, so that the dir structure like this is possible:

...
- components
  - domain
    - domain-component-a
    - domain-component-b
  - services
    - service-component-a
    - service-component-b
...

Describe alternatives you've considered

1. Support for multiple workspaces (see Add support for multiple workspaces #431 and Don't implement support for multiple workspace #470). Now reverted.
2. The only workaround atm is prefixing the component names, e.g. "domain-component-a". This sucks a bit, since the separator options are limited to - and _, since a component name have to be a valid file name.

Additional context
Already discussed this feature in Slack channel and here as a partial alternative to multiple workspaces support.

[AlexMoskvichev]

Hi. Want to support this issue.

I'm evaluating polylith for a few weeks now.

I've started trial project, structure in overall looks very good,
but I started wondering, how to organize components.
There is several aspects - number of components growing,
we have several layers of components - small utility components,
low level components, bigger components aka modules (but still components for the bases) etc.

As I'm new to poly, I can't argue for a specific solution,
but both adding tree structure (or at least sub levels) and
extracting lower layers to another workspace looks good for me.

The way of adding some prefixes to the component names I don't like very much.

I'm talking about a project with 50-200 components. For smaller number still nice to have add groups of components, but not that critical.

What are you think? Maybe we can add some metadata to the component's deps.edn or other config file and use them instead of relying on catalogs names?