[llvm] [LV][NFC] Add option to control debug printing of cost per lane (PR #201824)

[David Sherwood via llvm-commits]

david-arm wrote:

In order to use APFloat for printing out the number I will also the changes from https://github.com/llvm/llvm-project/pull/201560 because using APFloat leads to a large number of diffs in the file llvm/test/Transforms/LoopVectorize/WebAssembly/memory-interleave.ll. I'd rather not manually go through each one fixing them, and would prefer instead to auto-generate the CHECK lines. In this case I will have to land part of PR #201560 first that adds the flag to control printing of metadata, then once that lands rebase this PR on top.

https://github.com/llvm/llvm-project/pull/201824