Automation and optimization work

[sheepman4267]

This is the (long-awaited) appstream automation PR!

Here's what it does:

• Adds an Ansible playbook which automates steps 1-5 of the current "Regenerating from teaparty server directly" workflow
• Optimizes the creation of appstream metadata by symlinking every package to be analyzed into one directory. This script:
  • Avoids analyzing packages we don't need to (-currently the script ignores -dbginfo packages, but should probably also ignore -devel ones).
  • Only symlinks packages which are actually in the index, which works around Doesn't always cleanup stale eopkgs from deprecated packages ferryd#17.

Here's what it doesn't include yet, which it needs to before this can be marked ready for review:

• A Taskfile with further automation, including step 7 of the current instructions.
• Updates to README.md documenting the new process.
• A test plan in the description :)

Here's what it doesn't include, and I have no plans to:

• I don't plan to replicate step 6 of the current instructions in this new workflow. I have thoughts on more automated testing, but 1: The playbook already checks that the generated metadata file's packages are all in the eopkg index, and 2: testing of the new appstream data should happen as part of the package update test plan anyway. IMO, testing it here makes it more likely that someone will become lax when testing the package update, which it probably where it's more likely to go wrong anyway.
• Automation of the package update and PR process for appstream-data in the packages repo. On further reflection, I think any approach I can come up with there will be overly brittle and out of scope for this repo. That work will be done, but in a separate Taskfile in that package's files.

Test Plan
Follow the directions in the updated version of the README. That documentation is under test along with the actual process changes.

For reference, the current workflow is under the heading "Regenerating from teaparty server directly" in this repo's README.