Document `hack/ci/ci.sh` for running tests in a local VM via lima

[Honny1]

hack/ci/ci.sh sys remote rootless fedora-current runs tests in the same VM as CI, useful for reproducing CI failures locally. This should be documented in test/README.md. Requires lima to be installed.

#28946 (review)

[timcoding1988]

i don't think there is way to run the same vm. the github runner is hosted CNCF and we don't have access to those resource. but we definitely can add some debug step

[Luap99]

@timcoding1988 Well that is the point of hack/ci/ci.sh, so that anyone can run this locally if they have lima. All the main tests run inside that VM the host system should not matter.
There are of course things that we cannot run in the VM but that is only some part.

[mvanhorn]

Implemented in #29033