[Feature Request] Don't check KVM in `tools/devtool checkstyle`

[zulinx86]

Branched from issue #4747 .

Feature Request

Since tools/devtool checkstyle only checks coding style, it doesn't require KVM, but it does the KVM existence check. That prevents users from running it on their development env without KVM.

Describe the desired solution

Currently, it just calls cmd_test() that does the KVM check.

https://github.com/firecracker-microvm/firecracker/blob/main/tools/devtool#L900-L902

cmd_checkstyle() {
    cmd_test --no-build -- integration_tests/style -n 4 --dist worksteal
}

https://github.com/firecracker-microvm/firecracker/blob/main/tools/devtool#L686

cmd_test() {
// snipped
    ensure_kvm
// snipped
}

We might be able to add a new option of cmd_test() to bypass the check.

Describe possible alternatives

An alternative could be hardcoding a simplified version of cmd_test in cmd_checkstyle.

Additional context

N/A

Checks

• [x] Have you searched the Firecracker Issues database for similar requests?
• [x] Have you read all the existing relevant Firecracker documentation?
• [x] Have you read and understood Firecracker's core tenets?