samples: net: add Ethernet bridge sample

Added Ethernet bridge sample and enable mimxrt1180_evk_mimxrt1189_cm33
board as an example. On mimxrt1180_evk_mimxrt1189_cm33, 5 ports are
bridged with DHCPv4 enabled to test, including 4 DSA ports and
1 normal Ethernet port.

Signed-off-by: Yangbo Lu <yangbo.lu@nxp.com>