OIDC: Store the refresh token

[kerryarchibald]

Store the refresh token obtained during login somewhere good, probably close to the accessToken.

AC:

• the refresh token is stored like access token
  • try to encrypt with pickle key
  • try to save in idb
  • finally, save in localstorage
• the refresh token is cleared whenever the access token is cleared

[kerryarchibald]

Closed by matrix-org/matrix-react-sdk#11249