Enhance specifying the mandatory "platform" arg for multi arch images

[saisatishkarra]

Syft version after 0.75 fails to generate SBOM for multi-arch images and requires explicitly specifying the --platform option even when using the SHA specific to architecture.

Enhance specifying the --platform option when scanning images as an input arg to the Syft arguments.

New Feature PR on Syft that is causing the problem: anchore/syft#1801

How to reproduce:

Syft packages -v image:tag@sha256:<any-non-amd64-arch> -o spdx-json > sbom.spdx.json 
Error: * failed to construct source from user input image:tag could not fetch image: unable to use DockerDaemon source: image has unexpected architecture "arm64", which differs from the user-specified architecture "amd64

[willmurphyscode]

Thanks for opening this issue! The underlying issue in stereoscope has been fixed, see anchore/stereoscope#188. Once we do a syft release that pulls in the stereoscope fix, probably early next week, this issue should be fixed as well.