Correctly handle `SecurityException` for `acquireContentProvider` (#1622)

* Handle `SecurityException` for `acquireContentProvider`

* Added optional `throwOnMissingPermissions` arg to `acquireContentProvider`

Signed-off-by: Arnau Mora <arnyminerz@proton.me>

* Set `throwOnMissingPermissions` to `true`

Signed-off-by: Arnau Mora <arnyminerz@proton.me>

* Adapt comments, remove now unnecessary try/catch in AccountSettingsMigration20

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Signed-off-by: Arnau Mora <arnyminerz@proton.me>
Co-authored-by: Ricki Hirner <hirner@bitfire.at>