Capsules / Add fwupd support / Windows support

[mkopec]

Implement Windows support in the Capsule-on-Disk plugin in fwupd.

• Implement CoD plugin for Windows (see Capsules / Add fwupd support / Windows evaluation #1433 (comment))
  • Add implementation of efivar code for Windows
  • Stage the capsule onto the ESP
  • Set OsIndications correctly for Capsule Update
  • Implement platform reset after staging the capsule
  • Submit for upstream early to ensure we're aligned with what upstream wants
    • PRs for reference: Enable building uefi-capsule plugin on FreeBSD  fwupd/fwupd#3258, Update ESRT access implementation for FreeBSD fwupd/fwupd#3343
  • Add self-tests
• Document the process of installing fwupd on windows and using it to perform updates

Capsule-on-Disk is specifically used to avoid issues with having the Windows Bootloader stage the update for us.