[llvm] [libc] [libc] Move printf long double to simple calc (PR #75414)

[via llvm-commits]

michaelrj-google wrote:

@gchatelet and @lntue do you have any comments before I land this? I'm going to let it run with the fuzzer for a while to check correctness.

https://github.com/llvm/llvm-project/pull/75414