Add rp235x imagedef features (based on rp2040 boot2 features)

rp235x firmwares need an Image Definition if they want to be called
from the rp235x bootrom.

Currently this Image Definition is manually added to each project/example,
but for most users it will always be the default (Secure Exe).

This commit adds crate features to allow users to configure this, with the
default of including a Secure Exe Image Definition in.
Just like the boot2-* features, this includes an opt-out (imagedef-none)
to allow the user to not make use of this included Image Definition.

0 files changed, 0 insertions, 0 deletions