Drop support for deprecated security report schemas

What does this MR do and why?

Related issue: #351003 (closed)

We now have directories for each supported schema version:

lib/gitlab/ci/parsers/security/validators/schemas structure

gitlab/lib/gitlab/ci/parsers/security/validators/schemas on  master ➜ tree -L 2
.
├── 14.0.0
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.1
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.2
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.3
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.4
│   ├── cluster-image-scanning-report-format.json
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.5
│   ├── cluster-image-scanning-report-format.json
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.0.6
│   ├── cluster-image-scanning-report-format.json
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.1.0
│   ├── cluster-image-scanning-report-format.json
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── 14.1.1
│   ├── cluster-image-scanning-report-format.json
│   ├── container-scanning-report-format.json
│   ├── coverage-fuzzing-report-format.json
│   ├── dast-report-format.json
│   ├── dependency-scanning-report-format.json
│   ├── sast-report-format.json
│   └── secret-detection-report-format.json
├── dependency-scanning-report-format.json -> 14.0.0/dependency-scanning-report-format.json
├── sast-report-format.json
└── secret-detection-report-format.json

so we simply remove the ones that are not in a versioned subdirectory. In lib/gitlab/ci/parsers/security/validators/schema_validator.rb we added PREVIOUS_RELEASES which listed versions of https://gitlab.com/gitlab-org/security-products/security-report-schemas/-/tags which we consider unsupported in %15.0. We also used Sisense to determine other versions of the security report schema were used (KNOWN_VERSIONS_TO_REMOVE) and marked them for being unsupported as well (VERSIONS_TO_REMOVE_IN_15_0).

From %15.0 we will enforce schema validation and reports that use a version that's NOT in SUPPORTED_VERSIONS or DEPRECATED_VERSIONS will not be ingested. Reports using DEPRECATED_VERSIONS will emit a warning.

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