feat!: core managed components functionality

[mmikita95]

• Moving Component, ComponentTree and SessionComponentTree classes to a separate ui_utils file.
• StreamsyncUI class responsible for creating components and attaching them to ComponentTree
• StreamsyncUIManager class intended as a "user-facing" interface
• Tests for UI manager

[ramedina86]

Looks good to me but I'd really prefer having @FabienArcellier 's review before merging

[FabienArcellier]

Thanks, it's a great step forward.

We have to cover this pattern :

import streamsync as ss

with ss.init_ui() as ui:
  with ui.Page("other page"):
    ui.Text(text='Hello Pigeons')

[raaymax]

question: is this intended?
class StreamsyncUI is in ui_manager.py
and class StreamsyncUIManager in in ui.py

[mmikita95]

I see how this can be confusing. My logic was that ui_manager contains an "actual manager class" (StreamsyncUI), and ui provides easy access to the interface (from streamsync.ui import StreamsyncUIManager) that user is supposed to build upon. Hence the discrepancy in the class names and file names – ui_manager is reserved for internal use, and ui is "out-facing", while the class names are vice versa, so that StreamsyncUIManager could give a user a better hint on what it is supposed to do.
I think we might change that though, because, after contemplating on it, doesn't seem like the best choice.