Add internal telemetry for identifying when the file source is reading to EOF for deleted files

[neuronull]

Users come across the behavior described in #11742 , and part of the problem is there is not much telemetry that Vector provides users to help understand what might be causing the behavior they are seeing.

This issue represents the work to add this internal telemetry. Note that due to the nature of the code in question , the implementation will need to be performant and will need to be performance tested.