Fix `testtype` Makefile target

When running make testtype, there currently are multiple issues:

• test_lzw_decoder_large_stream_performance runs into a timeout, stopping the whole process (setting it to 60 seconds let the tests continue).
• 701 out of 492 tests failed with some common error messages which would have to be collected.

As having broken development tooling does not make sense, the following steps should be performed:

• Determine the types of errors
• Evaluate the impact of the errors
• Check which errors can be fixed and fix them
• Check how to continue with these checks. Are they useful enough to get a CI run? Are they irrelevant and should be cleaned up completely?