docker: Add support for vendor_kernel_boot images

Description

Latest Pixel devices require vendor_kernel_boot in order for recovery to boot up. This is along side vendor_boot, boot partitions.

Issue(s)

https://gitlab.e.foundation/e/backlog/-/issues/7464

Test environment

https://gitlab.e.foundation/e/priv/os/build/-/pipelines/345543

Test procedures

Technical details

Screenshots

Check list

• Self review
• Test procedure explained
• Tested on fresh install
• Tested applied as an update
• License
• Internal documentation
• User documentation