Secure boot abstraction merge 2

[alexgg]

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[alexgg]

@resin-jenkins retest this please

[alexgg]

lgtm

[alexgg]

@resin-jenkins retest this please

[alexgg]

*qemu-generic-aarch64 passed tests

• The rest seem to be aborted before completion

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

@resin-jenkins retest this please

[alexgg]

Merged as part of https://github.com/balena-os/meta-balena/pull/3295