WIP: enhance OVAL check for applicability in bootc env

[vojtapolasek]

Description:

• check also for presence of /run/ostree-booted file
• I made modifications to both OVAL files - one in shared/applicability/oval, another in shared/checks/oval, I am not sure when the shared/checks/oval/bootc.xml is used, but I think it is a good idea to keep them in sync

Rationale:

• current conditions can be quite easily met by regular OS not actually running from ostree, just by installing / removing appropriate packages

• this PR makes the applicability stricter, although not bulletproof

• Fixes Bootc detection easily matches non-bootc systems #13990

Review Hints:

Build content not including this PR:

1. Run a RHEL VM, install rpm-ostree, bootc
2. oscap xccdf eval --profile stig --rule xccdf_org.ssgproject.content_rule_enable_dracut_fips_module ssg-rhel9-ds.xml

This should result in "not applicable", although it should be applicable.

Build the content with this PR and repeat steps above.

The result will be probably "fail", but definitely not "not applicable".