tests: bluetooth: tester: Fix bluetooth tester for nucleo_wba55cg

Fix compilation error by specifying usart1 to be used for uart-pipe.
Add a board-specific configuration file to disable the console,
so, the usart1 will be used only for bluetooth and to specify
the BT_HCI_TX_STACK_SIZE.

Signed-off-by: Nidhal BEN OTHMEN <nidhal.benothmen@st.com>