Fix N+1 queries for issues search

What does this MR do?

Related to #230712 (closed)

• Add preloading for project.project_feature (as reported by bullet), project.route, project.namespace and project.namespace.route

• Update spec to remove threshold for the ActiveRecord::QueryRecorder check

Note: even though the spec changes are only in EE, the changes apply to both CE and EE

Screenshots (strongly suggested)

before

after

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
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  • I have not included a changelog entry because _____.
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

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• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team