Include whether Beat is running from a FIPS distribution in User Agent

[ycombinator]

What does this PR do?

This PR enhances the useragent.UserAgentWithBeatTelemetry function to take in an additional argument, isFIPSDistribution bool and include FIPS in the user agent set by Beats if this argument is set to true.

Why is it important?

To track FIPS usage in Beats.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have added tests that prove my fix is effective or that my feature works

[elasticmachine]

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