Add 'Prefer CVE filenames to GHSA filenames lint rule and rename 4 advisories

Author: jasnow

gems/nokogiri/GHSA-v6gp-9mmm-c6p5.yml renamed to gems/nokogiri/CVE-2018-25032.yml

@@ -77,4 +77,5 @@ patched_versions:
   - ">= 1.13.2"
 related:
   cve:
+    - 2021-30560
     - 2022-23308

gems/nokogiri/GHSA-fq42-c5rg-92c2.yml renamed to gems/nokogiri/CVE-2021-30560.yml

@@ -41,6 +41,12 @@
       expect(advisory['cve'] || advisory['osvdb'] || advisory['ghsa']).not_to be_nil
     end
 
+    it "should CVE-XXX if cve field has a value" do
+      if advisory['cve']
+        expect(filename).to start_with('CVE-')
+      end
+    end
+
     describe "platform" do
       subject { advisory['platform'] }