Revert file suffix change for output files

[gessulat]

MSAID's streaming feature introduced a regression so that the suffixes of the psms output files are not psms.txt anymore but only psms. This is not desirable because it makes it harder for users to understand what what kind of file the output really is.

@jspaezp suggested, to instead use psms.csv or psms.tsv as .txt files are usually space separated while csv and tsv are comma and tab separated respectively.

TODO

• [ ] replace all suffixes for output files such as psms and other levels (precurors, peptides, etc) with {level}.tsv