[processor/resourcedetection] Add fail_on_missing_metadata to EC2 detector

[atoulme]

Description

Add fail_on_missing_metadata option on EC2 detector

If the EC2 metadata endpoint is unavailable, the EC2 detector by default ignores the error.
By setting fail_on_missing_metadata to true on the detector, the user will now trigger an error explicitly,
which will stop the collector from starting.

Link to tracking issue

Relates to #35936

[pjanotti]

LGTM. I wonder if a similar generic option should be available to all resource processors: the fact that one can start and not have the proper attributes can be considered an error in many scenarios.

[atoulme]

LGTM. I wonder if a similar generic option should be available to all resource processors: the fact that one can start and not have the proper attributes can be considered an error in many scenarios.

there is no uniform behavior for all detectors, that can be a followup issue for the processor as a whole.

[andrzej-stencel]

@atoulme Can you resolve the conflicts? This is probably the other PR of yours #37451.

[atoulme]

Thanks! Rebased.