BUG(multi): Grouping by resource doesn't work in multi resource mode

[doronkg]

Describe the bug
Kor version v0.4.0 introduced a new feature for grouping output by resource: kor all --group-by=resource.
When grouping by resource in multi resource mode (e.g. resource_a,resource_b), the output is grouped by namespace (default).

To Reproduce
Run kor resource_a,resource_b --group-by=resource.

Expected behavior
The resources will be grouped by resource and not by namespace.

Screenshots

OS version, architecture and kor version
Kind v0.22.0 Windows/amd64, OpenShift v4.14.22 Linux/amd64
Kor version: 0.4.1

Additional context
#256

[yonahd]

Looks like the support for this was not built in for non table format. We need to add the support

[doronkg]

Looks like the support for this was not built in for non table format. We need to add the support

It is not supported neither in table format.

[doronkg]

/assign
WIP in #320