[kots]: add a kernel version check to the preflights

[mrsimonemms]

Description

Add a preflight check to ensure that the kernel version is 5.4.0 or above. It includes preflight checks, so that 5.4.0-gke would return as valid.

Related Issue(s)

Fixes #8862

How to test

Deploy via KOTS.

To check the functionality, run some of the followings:

docker run --rm alpine/semver semver --coerce --range '>=5.4.0' 5.13.0-1019-gcp // valid
docker run --rm alpine/semver semver --coerce --range '>=5.4.0' 5.4.0-1009-gcp // valid
docker run --rm alpine/semver semver --coerce --range '>=5.4.0' 5.3.9-1009-gcp // errors - would return "invalid"

Release Notes

[kots]: add a kernel version check to the preflights

Documentation

[mrsimonemms]

As a follow-up, have checked with Barry @ Replicated whether this image will automagically get added to the list of airgapped images or whether we need to add it to additionalImages list in kots-app.yaml

[corneliusludmann]

looks good to me