K PL Tutorials are out of date

[Baltoli]

The languages in 2_languages are slightly out of date and should be modernised. A list of concrete issues identified is:

• Inconsistency in SIMPLE language tutorial #2999
• test suite emits warnings on macro labels placed on rules #2882 (partially fixed for the regression test suite, not for the PL tutorial)

Some work has been done already:

• Update simple-untyped to work with the modern backends. #2841

[radumereuta]

This should be fixed now: #3168