Fix autofix replacements & rework test pipeline

[Splines]

We fix missing back-transformations of some ERB statements in lintex text. For this purpose, we introduce a Dummy Replacements Map that tracks the replacements we made.

With this new change, we notice that maintaining manual tests for the offset map is really a huge pain. We get rid of that here and instead write some integration tests that cover the whole picture including pre- and postprocessor. This is even better since we now know exactly what failed in tests instead of having to manually parse the message objects and their fix ranges.