Bluetooth: Shell: Improve command `bt connections` to support BR conn

When execute `bt connections`, only the peer device address of selected
LE connection is flagged with `*`.

Improve the command `bt connections` to support BR connections.
Regardless of the connection type, `*` will be shown to indicate the
peer address of the current connection if the peer device address is
the peer address of selected connection.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>