serial: introduce CONFIG_UART_USE_RUNTIME_CONFIGURE

This kconfig option enables runtime configuration of UART
controllers. This allows application to call uart_configure()
to configure the UART controllers and calling uart_config_get()
to retrieve configuration. If this is disabled, UART controllers
rely on UART driver's initialization function to properly
configure the controller. The main use of this option is mainly
code size reduction.

Fixes #16231

Signed-off-by: Daniel Leung <daniel.leung@intel.com>