Adapt OAuth2 implementation to Matrix Spec v1.18 (#34026)

* Adapt OAuth2 implementation to Matrix Spec v1.18

* Handle more cases of oidc->oauth

* Fix test

* Fix read back of oauth2 context

* Iterate

* Fix tests

* Discard changes to apps/web/playwright/e2e/settings/account-user-settings-tab.spec.ts

* Fix test

* Fix test

* Fix test

* Potential fix for pull request finding 'Unused variable, import, function or class'

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* Iterate

* Iterate

* Fix test

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apps/web/package.json

@@ -87,7 +87,6 @@
         "matrix-widget-api": "^1.16.1",
         "memoize-one": "^6.0.0",
         "mime": "^4.0.4",
-        "oidc-client-ts": "^3.0.1",
         "opus-recorder": "^8.0.3",
         "pako": "^3.0.0",
         "png-chunks-extract": "^1.0.0",