msw: continue handler migration

[deer-wmde]

• sets onUnhandledRequest: 'error' so that not-implemented handlers error instead of bypass msw (docs)
• migrates remaining existing handlers + some policy ones needed for interaction
  • POST /api/wiki/entityImport
  • GET /api/wiki/entityImport
  • POST /api/wiki/create
  • POST /api/wiki/delete
  • POST /api/wiki/logo/update
  • POST /\/api\/wiki\/setting\/.*?\/update$/
  • POST /api/wiki/details
  • GET /api/wiki
  • GET /api/v1/policies/missing
  • GET /api/v1/policies/current
• fixes removeWiki: splice() mutates, not copies (docs)
• fixes user login handle, not always test@local anymore
  • do we actually want this or are we now relying on it? :D

Almost ready for review but needs a merge & rebase of #1184

https://phabricator.wikimedia.org/T436530

[github-actions]

Deployment previews on netlify for branch refs/pull/1186/merge will be at the following locations (when build is done):

• UI with mock store: https://c58112324a-mock--wbstack-ui.netlify.app/
• UI pointing to prod: https://c58112324a-prod--wbstack-ui.netlify.app/