clang-tidy: disabled readability-identifier-length

clang-tidy 14 now supports the readability-identifier-length check which warns about too short variable names, see https://releases.llvm.org/14.0.0/tools/clang/tools/extra/docs/clang-tidy/checks/readability-identifier-length.html

In general, users should be encouraged to use better names than "i" but at this point, this is raising too many warnings.