smpmgr: upload: add --bypass-inspection option for non-MCUboot images

[axelnxp]

As done for the upgrade command, allow to upload non-MCUboot images.

It was discussed in #92 the following with @JPHutchins :

I'd like to merge this and then I will follow up to make the following changes to the API before releasing:

* remove `--bypass-inspect` option

* replace it with an optional `--image-type=<image type>` field

* default `--image-type` to `"mcuboot"`

* allow `--image-type=unknown` to do exactly what `--bypass-inspect` does now

The goal is to support multiple image types in the long run rather than ignoring everything that is not mcuboot.

LMK if that sounds OK.

As this hasn't be implemented yet, I propose to add a similar bypass mechanism to the upload command until the final rework.

[JPHutchins]

Thank you!