[embeddable rebuild] remove legacy embeddable system

[nreese]

• Remove embeddable.registerEmbeddableFactory, preventing legacy embeddable registration - small
• Update dashboard "Add from library" to remove usage of legacy embeddables - small
• Update dashboard "Add panel" to remove usage of legacy embeddables - small
• Update Canvas "Add from library" to remove usage of legacy embeddables - small
• Update Canvas "Add panel" to remove usage of legacy embeddables - small
• Remove usage of getEmbeddableFactory in DashboardContainer.addNewPanel - small
• Remove usage of getEmbeddableFactory in DashboardRenderer - small
• Remove usage of getEmbeddableFactory in migrateDashboardInput - medium. Question: how will migrations be run for legacy panels replaced by new react embeddable panels?
• Remove legacy embeddable registry and getter methods - small
• Refactor DashboardContainer so that it no longer implements Container interface - large
• Remove Container interface - small
• Remove Embeddable interface and all associated types like EmbeddableInput and EmbeddableOutput - large since there may be unexpected usages of these classes throughout Kibana.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)

[ThomThomson]

Hey @nreese should we maybe put this list in #180058 instead of creating a new issue?

[nreese]

Closing, moved task list to existing cleanup issue #180058