[$] Python, tail calls, and performance

Ken Jin welcomed EuroPython2025 attendees tohis talk entitled "Building a new tail-calling interpreter for Python", butnoted that the title really should be: "Measuring the performance ofcompilers and interpreters is really hard". Jin's efforts to switch the CPython interpreter to use tail calls,which can be optimized as regular jumps,initially seemed to produce an almost miraculous performance improvement.As his modified title suggests, the actual improvementwas rather smaller; there is still some performance improvement andthere are other benefits from the change.