Review usage of Reporter::InternalError, addresses BIT-1045.

Replaced some with InternalWarning or InternalAnalyzerError, the later
being a new method which signals the analyzer to not process further
input.  Some usages I just removed if they didn't make sense or clearly
couldn't happen.  Also did some minor refactors of related code while
reviewing/exploring ways to get rid of InternalError usages.

Also, for TCP content file write failures there's a new event:
"contents_file_write_failure".
Merge branch 'master' into topic/jsiwek/internal-errors
Merge remote-tracking branch 'origin/master' into topic/robin/internal-errors-merge
Pass over the InternalError() changes.
Renaming InternalAnalyzerError to AnalyzerError.

This is to avoid confusion when we abort and when not: InternalError()
aborts; AnalyzerError() does not.
Add check for curl command to active-http.test

Added a check if the curl command is available when running the
active-http.test so that it fails more quickly and with a clear error
message if it's not available.
Reverting one of the my internal errors tweaks.
Merge branch 'topic/robin/internal-errors-merge'

* topic/robin/internal-errors-merge:
  Reverting one of the my internal errors tweaks.
  Renaming InternalAnalyzerError to AnalyzerError.
  Pass over the InternalError() changes.
  Review usage of Reporter::InternalError, addresses BIT-1045.
Updating submodule(s).

 [nomail]
Updating submodule(s).

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Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  Add check for curl command to active-http.test

I've moved the check from TEST-EXEC to TEST-REQUIRES. I think it's
fine to just skip the test if curl is not available.
Updating submodule(s).

 [nomail]