fix: do not panic on an invalid image name regexp

IsImageMatched interpolates the image name from kustomization images[].name
straight into a regexp and discarded the compile error. When the name is not
a valid regexp (for example "["), regexp.Compile returns a nil *Regexp and
the following MatchString call dereferences it, so kustomize build crashes with
a SIGSEGV.

Capture the compile error and return false when it is set. A name that can't
compile matches no image, which leaves the resource untouched (the same result
you get for any name that doesn't match). Adds a unit test for the invalid name
and a krusty end-to-end case that builds without panicking.

Signed-off-by: Arpit Jain <arpitjain099@gmail.com>