test: abootimg: Add test for bootconfig handling

test: abootimg: Add test for bootconfig handling

Add test to verify that androidboot.* parameters are correctly extracted
from bootargs and appended to the bootconfig section when using
'abootimg get ramdisk' with boot image v4 and vendor_boot image.

The test verifies:
- androidboot.* parameters are removed from bootargs
- They are appended to the bootconfig section in the ramdisk
- Non-androidboot parameters remain in bootargs
- The bootconfig trailer is properly updated

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Guillaume La Roque (TI.com) <glaroque@baylibre.com>
Reviewed-by: Mattijs Korpershoek <mkorpershoek@kernel.org>
Link: https://lore.kernel.org/r/20260112-bootconfig-v5-5-79b242159ac7@baylibre.com
[mkorpershoek: dropped whitespace changes from original patch]
Signed-off-by: Mattijs Korpershoek <mkorpershoek@kernel.org>