Sync state

[bmarty]

We stop the sync before login out here: https://github.com/element-hq/element-x-android/blob/main/libraries/matrix/impl/src/main/kotlin/io/element/android/libraries/matrix/impl/RustMatrixClient.kt#L466, but there are 2 problems:

• we do not start it again in case of logout failure (which is mitigated by the second problem)
• if there is network coverage, the sync is automatically started again here: https://github.com/element-hq/element-x-android/blob/main/appnav/src/main/kotlin/io/element/android/appnav/LoggedInFlowNode.kt#L179

We should probably let the MatrixClient expose a canStartSync flow to avoid the sync to be automatically started again by observeSyncStateAndNetworkStatus()

[bmarty]

We are not stopping the sync anymore, but instead we remove the client listener (done in #3480). So I guess we can close this issue.