Support per-port UART RX/TX swap parameters

Describe problem solved by the proposed feature

Reversed UART RX/TX wiring currently needs rewiring or custom firmware/startup configuration. There is no common per-port parameter for GNSS, MAVLink and other serial services.

Describe your preferred solution

Add reboot-required SER_<port>_SWAP booleans, defaulting to off. Apply hardware SWAP once before the assigned service starts. Initially enable this on Kakute H7 using the existing STM32H7/NuttX ioctl.

Describe possible alternatives

Rewire the device, use a custom startup command, or add separate settings to each protocol driver.

Additional context

Kakute H7 bench test: SWAP enabled checksum-valid UBX reception; disabling it stopped reception. Related serial configuration redesign: #28481.