Add support for version V2R5 of the DISA STIG ruleset

[georgibaltiev]

How to categorize this PR?

/kind enhancement

What this PR does / why we need it:
This PR adds support for version V2R5 (download link) of the DISA STIG ruleset. There are only 2 minor differences compared to version V2R4, considering the deprecation of the following two rules: [242386 and 242388].

The deprecation of the two rules can be checked via the revision history file (./U_Kubernetes_V2R5_Revision_History.pdf'):

- CNTR-K8-000320, CNTR-K8-000340 -
Deleted requirement. Insecure-port and
insecure-bind-address flags were fully
removed and no longer exist.
- Rule numbers updated throughout due to
changes in content management system.

Since Diki supports at most two versions of a ruleset simultaneously, support for version V2R3 is dropped with this PR as well.

Which issue(s) this PR fixes:
Fixes #680

Special notes for your reviewer:
The documentation still advises the users to use version V2R4 if they run Diki via the CLI. An additional PR bumping the documentation will be added once we do a release containing the support for V2R5.

Release note:

Diki no longer supports version V2R3 of the DISA STIG ruleset.

Diki now supports version V2R5 of the DISA STIG ruleset.

[gardener-prow]

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