doc: scobc_a1: Rename board name

Rename the board name to `scobc-a1`, and update the board's full name
to `SC-OBC Module A1`. And update the output of the `Hello World`
sample to match the latest Zephyr version.
Then, The supported feature section was replaced with a hw-directive
block.

Signed-off-by: Takuya Sasaki <takuya.sasaki@spacecubics.com>