refactor: localStorageのaccountsはindexedDBで保持するように (#7609)

* accountsストアはindexedDBで保持するように

* fix lint

* fix indexeddb available detection

* remove debugging code

* fix lint

* resolve https://github.com/misskey-dev/misskey/pull/7609/files/ba756204b77ce6e1189b8443e9641f2d02119621#diff-f565878e8202f0037b830c780b7c0932dc1bb5fd3d05ede14d72d10efbc3740c
Firefoxでの動作を改善

* fix lint

* fix lint

* add changelog