[META] Convert CivicTheme to use Single Directory Components (SDC)

Problem/Motivation

This meta issue is for planning out the tasks for updating CivicTheme to use Single Directory Components (SDC).

Steps to reproduce

Proposed resolution

Research and determine approach, document approach, and implement.

Remaining tasks

• Research and prototype approach and create technical direction [needs issue]
• Update build system to separate CSS/JS assets [needs issue]
• #3464542: Create SDDS project SDC conversion guide
• Update existing components [needs issues] (prioritize the components needed for Barcelona)
• Test each component with Experience Builder [needs issues]
• TBD: Test each component without Experience Builder [needs issues]

User interface changes

The UI for these components should be the same as in CivicTheme 1.8, i.e. the SDC migration should not affect any CivicTheme functionality or look-and-feel.

API changes

Data model changes