roles/kvm: fix option description eval

[osnyx]

literalExpression was not taken from lib and hence caused the fc-search eval to fail.

I also checked all other occurances of literalExpressions in the platform code. Almost all of them ar placed after a global with lib; which is bad style but at least causes them to eval fine.

Part of fixing the fc-search eval for 24.11. Not necessarily complete.

PL-133423

@flyingcircusio/release-managers

Release process

• Created changelog entry using ./changelog.sh: no, cosmetic change

PR release workflow (internal)

• PR has internal ticket
• internal issue ID (PL-…) part of branch name
• internal issue ID mentioned in PR description text
• ticket is on Platform agile board
• ticket state set to Pull request ready
• if ticket is more urgent than within the next few days, directly contact a member of the Platform team

Design notes

• Provide a feature toggle if the change might need to be adjusted/reverted quickly depending on context. Consider whether the default should be on or off. Example: rate limiting.
• All customer-facing features and (NixOS) options need to be discoverable from documentation. Add or update relevant documentation such that hosted and guided customers can understand it as well.

Security implications

• Security requirements defined? (WHERE)
  • ensure proper documentation on search.flyingcircus.io: fc-search needs to eval the 24.11 platform
• Security requirements tested? (EVIDENCE)
  • existing automated tests still pass
  • fc-search.service displays the first occuring eval failure. This one is fixed, let's move forward one at a time.

[leona-ya]

that's not really the use case for literalExpression, as this is not a parseable nix-string, but fine for me for fixing the eval.