adding explicit migration plans (#1189)

* adding explicit migration plans
* consistency update
* adding in Swift Language Guides section and archive
* Update _info-architecture/0003-swift-docs-proposal.md

Co-authored-by: Franz Busch <privat@franz-busch.de>

* shifting to leveraging steering groups for review delegation

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Co-authored-by: Franz Busch <privat@franz-busch.de>

Author: heckj