fix: VulnerabilityFinding equality should exclude other record types

Our previous comparison between finding records did not properly check
the class type to ensure non-finding records are properly excluded. This
can occur when multiple records are created within a transaction (such
as `Vulnerabilities::CreateService` and a simple `Array#uniq` check is
performed.

https://gitlab.com/gitlab-org/gitlab/-/issues/332825

Changelog: fixed
EE: true

ee/app/models/vulnerabilities/finding.rb

@@ -336,6 +336,7 @@ module Vulnerabilities
     alias_method :==, :eql?
 
     def eql?(other)
+      return false unless other.is_a?(self.class)
       return false unless other.report_type == report_type && other.primary_identifier_fingerprint == primary_identifier_fingerprint
 
       if ::Feature.enabled?(:vulnerability_finding_tracking_signatures, project) && project.licensed_feature_available?(:vulnerability_finding_signatures)

ee/spec/models/vulnerabilities/finding_spec.rb

@@ -1055,6 +1055,11 @@ RSpec.describe Vulnerabilities::Finding do
         expect(finding1.eql?(finding2)).to be(vulnerability_finding_signatures_enabled)
       end
 
+      it 'wont match other record types' do
+        historical_stat = build(:vulnerability_historical_statistic, project: project)
+        expect(finding1.eql?(historical_stat)).to be(false)
+      end
+
       context 'short circuits on the highest priority signature match' do
         using RSpec::Parameterized::TableSyntax