Automatically try to rebase TrenchBoot patches on top of the QubesOS patches

[DaniilKl]

Is your feature request related to a problem? Please describe.

We need to build QubesOS packages that will contain both: Qubes patches for a specific component with TrenchBoot patches on top of it. And we need to constantly check whether the Qubes patches got updated and try to rebase if so, so the QubesOS users will have the the QubesOS packages with the newest Qubes patches with newest TrenchBoot patches on top of it.

Is your feature request related to a new idea or technology that
would benefit the project? Please describe.

We should consider some rebase automation in the projects's CI/CDs.

Describe the solution you'd like

The latest TrenchBoot patches should be automatically periodically rebased on the latest QubesOS patches (or semi-automatically, in case of conflicts) for the following components:

• vmm-xen
• grub2
• antievilmaid

[DaniilKl]

The following PRs should address this issue:

• .github: workflows: add rebasing workflows grub#32
• .github: workflows: rebase-and-build.yml: add qubes-antievilmaid#15
• .github: workflows: rebase-and-build.yml: add xen#26
• docs: dev-docs: QubesOS-packages-sync.md: add TrenchBoot.github.io#59