Limit security policy to a file

What does this MR do?

This MR is created to address performance concerns that are raised in !54419 (merged)

It essentially does two things

• Check only one file as policy file
• Allow only 5 policy to be enabled

Related issue

#325839 (closed)

Does this MR meet the acceptance criteria?

Conformity

• 📋 Does this MR need a changelog?
  • I have not included a changelog entry because changes behind the ff. (https://about.gitlab.com/handbook/engineering/ux/technical-writing/workflow/#when-documentation-is-required))
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