Bump supported LLVM range from 10 through 15 to 11 through 16
LLVM 15 turns on the new pass manager by default, which we have yet to
migrate to so for new we pass the -enable-new-pm-0
flag in our
llvm-passes flag.
LLVM 11 was the first version to support the -enable-new-pm
flag so we
bump the lowest supported version to 11.
Fixes #21936 (closed)