binman: Add a test for nested and aligned sections

binman: Add a test for nested and aligned sections

Current test coverage is likely sufficient for the logic used to place
sections in the image. However it seems useful to add a test specifically
for nested sections, since these could have some unusual interactions.

Add a new test for this and aligned sections. This test failed before the
refactor to drop the bsection.py file (Section class), but passes now.

Signed-off-by: Simon Glass <sjg@chromium.org>