Exposed detection count in gvafpscounter for internal use

[pbartosik]

Description

Part of effort to facilitate further pipeline validation in Optimizer. Exposing the statistic as part of gvafpscounter and marking it as internal use was deemed the best approach for now.

Fixes # (issue)

Any Newly Introduced Dependencies

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How Has This Been Tested?

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Checklist:

• I agree to use the MIT license for my code changes.
• I have not introduced any 3rd party components incompatible with MIT.
• I have not included any company confidential information, trade secret, password or security token.
• I have performed a self-review of my code.