Bluetooth: Host: Fix connection establishment upon RPA timeout

Before this commit, the following bugs were present:
- When `CONFIG_BT_FILTER_ACCEPT_LIST` was set, connection establishment
  was cancelled upon RPA timeout. This required the application
  to restart the initiator every RPA timeout.
- When `CONFIG_BT_FILTER_ACCEPT_LIST` was not set, the RPA was not updated
  while the initiator was running.

This commit unifies the RPA timeout handling for both these cases.
Upon RPA timeout the initiator is cancelled and restarted when
the controller raises the LE Connection Complete event.
The workqueue state is checked when restarting the initiator to prevent
it being restarted when the timeout is hit.

Corresponding test cases have been added to ensure that this
feature works.

Signed-off-by: Rubin Gerritsen <rubin.gerritsen@nordicsemi.no>