WIP: Server-side rendering

[pskelin]

tasks:

• pskelin: rebase
• vladi: move async logic from processChildren to connectedCallback (see chore: make processChildren sync #9890)
• vladi: isSsr checks - productive cleanup
• refactor lifecycle so common steps are in single methods
  • constructor
  • connectedCallback
    • processChildren is used in ssr
  • updateAttrbitues
  • updateShadowRoot returns string
• pskelin: h-ssr - rethink where it is and integration with wrapper
• ilhan: assets - import json works in nodejs only with {with:{type:"json"}})).default;
• nayden: automated testing setup (test with clientside hydration)
• nayden: UI5element hydrate - chore: enable hydration for declarative shadow DOM components #11488
• ilhan: component specific usecases (button + select) - introduce isClientAPI
• ilhan: Extend DOM shims (children/childNodes) (or via better separation of SSR checks)
• i18n works, render with different theme
• styles - only inline
  • add links (CSP like)
• app integration
  • how to instert all framework styles
  • wrappers to trigger rendering