Meta issue: clean up redundant compat code

[hugovk]

Bug report

There's several places that have compatibility code for EOL and unsupported Python versions.

We can modernise the code by removing the obsolete bits.

I'll open separate PRs to keep the changes focused by area, and intend to use this meta issue for them all (but can also open separate issues if preferred).

Linked PRs

• gh-100176: venv: Remove redundant compat code for Python <= 3.2 #100177
• gh-100176: remove incorrect version compatibility check from clinic #100190
• gh-100176: Tools/iobench: Remove redundant compat code for Python <= 3.2 #100197
• gh-100176: Mac/build-installer: Remove redundant compat code for Python 3.5 and older #100297
• gh-100176: Remove outdated Tools/{io,cc,string}bench #101853

[sobolevn]

While looking at this, I got interested: do we even need https://github.com/python/cpython/blame/main/Tools/stringbench/stringbench.py ? It has some python2/3 compat code and the last changes to it was 10 years ago. It is clearly not up-to-date. I will raise this question on discuss.python.org

[sobolevn]

https://discuss.python.org/t/do-we-still-need-tools-io-cc-string-bench/22557