Initial migration of table-controls code from konveyor/tackle2-ui

[mturley]

• Migrates code from https://github.com/konveyor/tackle2-ui/tree/ded98a9/client/src/app/hooks/table-controls and other common paths in tackle2-ui
• Creates tackle2-ui-legacy directory for Konveyor-specific implementations that still need to be rewritten / refactored
• Installs @migtools/lib-ui for now, we will remove that dependency by copying over additional legacy code in a separate PR
• Fixes imported code to work with dependency versions from pf-extension-seed
• Converts documentation from OLD_DOCS.md to a new (mostly rewritten) pf-docs site with embedded examples
  • Some advanced examples are stubs that will be replaced in a separate PR
  • Also creates CONTRIBUTING.md for some extra maintainer-facing details that don't belong in consumer docs
  • Note that these efforts are not complete (some stuff is still in OLD_DOCS.md) but I don't want to block merging this so I will follow up on them in a separate PR
• Changes here compared to the code as it was in tackle2-ui:
  • Ran Prettier (the prettierrc config from pf-extension-seed is different from the one in tackle2-ui)
  • Fixed import paths
  • Removed dependency on react-i18n (leaving TODO comments in places where we should add support for custom text / future i18n)
  • Removed dependency on react-router-dom (was used by useUrlParams which now works directly with the browser history API instead)
  • Fixed type errors, lint errors and a11y report errors
  • Renamed hooks, helpers, types etc to fit the new table-batteries naming conventions
  • Misc general cleanup

The docs site can be previewed at https://react-table-batteries-staging.surge.sh/extensions/table-batteries