[RFE] Move out customizations out from portage-stable

[krnowak]

We want portage-stable to contain almost zero modifications, so we need to handle the following things:

• GLSA files
  • These files reside in the metadata/glsa directory.
  • They need to be moved elsewhere, but still at a place where glsa-check can find them.
  • I think we can keep them in portage-stable - metadata/glsa is a canonical location for GLSA stuff and the rsynced Gentoo repo has them there.
• bootstrap script
  • This file resides in scripts/bootstrap.sh.
  • Make our own copy of the bootstrap script and tell catalyst to use it.
  • Maybe our changes could be upstreamed?
    • Our changes were dropped as we don't build stage2 any more - Skip Catalyst stage2 as recommended by upstream Gentoo scripts#2153
• overridden usr-ldscript eclass
  • It's eclass/usr-ldscript.eclass.
  • Currently an empty file.
  • See if it can be either moved to coreos-overlay or vanilla version could be used, but some flag set to disable whatever it was doing.
  • Add eclass/usr-ldscript.eclass to package automation scripts#2373
  • We can sync it with Gentoo once we get rid of the split-usr USE flag in Flatcar.
• patched selinux-policy-2 eclass
  • Either drop the patch or upstream it.
  • Maybe the patch won't be necessary if we update our SELinux packages.
  • Done, whatever changes were needed, they got upstreamed.
• patched bash-completion-r1 eclass
  • The patch needs to be upstreamed to fix cross-compilation issues (putting completion files in wrong place).
  • The issue was fixed in Gentoo
• modified sys-apps/semodule-utils package
  • This adds a weak blocker on another package.
  • Most likely not needed any more.
• modified dev-util/perf package
  • The patch added support for python3.6.
  • Not needed, will go away when syncing with Gentoo.
• other eclasses (git grep -nie flatcar)
  • Most of the modifications add support for older EAPIs.
  • They are not necessary any more, and will go away when syncing with Gentoo.
• modified virtual/rust package (Move virtual/rust to coreos-overlay and drop the rust workflow flatcar-archive/portage-stable#313)
  • Updates are handled by automation, so needs to be moved to overlay.

The only change that we would have in portage-stable are:

• our repository configuration stored in metadata/layout.conf,
• our changelogs in the changelog directory,
• our name in profiles/repo_name,
• our markdown files (readme, maintainers, etc).

It's a part of #96.