feat(image): Buildkit support for misconfiguration scanning

[knqyf263]

Description

trivy image --image-config-scanners misconf doesn't work with Buildkit now. Images built by Docker have the /bin/sh -c prefix, while Buildkit doesn't.

$ docker history test
IMAGE          CREATED          CREATED BY                                       SIZE      COMMENT
b1afcbbdcdae   5 seconds ago    ADD foo.txt . # buildkit                         0B        buildkit.dockerfile.v0
<missing>      37 seconds ago   RUN /bin/sh -c ls # buildkit                     0B        buildkit.dockerfile.v0
<missing>      11 months ago    /bin/sh -c #(nop)  CMD ["/bin/sh"]               0B
<missing>      11 months ago    /bin/sh -c #(nop) ADD file:9bd9ea42a9f3bdc76…   7.46MB

Discussed in #5972

[DmitriyLewen]

It might make sense to add support for COPY instructions to buildkit.