Clean up ParseNumbers and fix perf regressions
Clean up ParseNumbers and fix perf regressions

- Fix formatting
- Replace char[] allocations with stackalloc
- Replace StringBuilders with FastAllocateString
- Tweak a few comparisons to make them leaner
- Tweak some tight loops to make them a bit leaner
- Help JIT to eliminate bounds checks on target spans
- Walk ptr destinations rather than indexing

kyulee1/coreclr,poizan42/coreclr,hseok-oh/coreclr,JosephTremoulet/coreclr,cshung/coreclr,ruben-ayrapetyan/coreclr,rartemev/coreclr,botaberg/coreclr,ruben-ayrapetyan/coreclr,botaberg/coreclr,ruben-ayrapetyan/coreclr,wateret/coreclr,kyulee1/coreclr,ruben-ayrapetyan/coreclr,hseok-oh/coreclr,wateret/coreclr,wtgodbe/coreclr,poizan42/coreclr,botaberg/coreclr,cshung/coreclr,rartemev/coreclr,wateret/coreclr,poizan42/coreclr,wateret/coreclr,JosephTremoulet/coreclr,poizan42/coreclr,yizhang82/coreclr,yizhang82/coreclr,hseok-oh/coreclr,cshung/coreclr,botaberg/coreclr,krk/coreclr,ruben-ayrapetyan/coreclr,JosephTremoulet/coreclr,yizhang82/coreclr,JosephTremoulet/coreclr,krk/coreclr,hseok-oh/coreclr,mmitche/coreclr,botaberg/coreclr,rartemev/coreclr,poizan42/coreclr,yizhang82/coreclr,wtgodbe/coreclr,wateret/coreclr,wtgodbe/coreclr,krk/coreclr,mmitche/coreclr,wtgodbe/coreclr,cshung/coreclr,botaberg/coreclr,cshung/coreclr,hseok-oh/coreclr,mmitche/coreclr,mmitche/coreclr,rartemev/coreclr,parjong/coreclr,poizan42/coreclr,JosephTremoulet/coreclr,rartemev/coreclr,yizhang82/coreclr,parjong/coreclr,wtgodbe/coreclr,parjong/coreclr,wateret/coreclr,parjong/coreclr,krk/coreclr,kyulee1/coreclr,hseok-oh/coreclr,wtgodbe/coreclr,JosephTremoulet/coreclr,krk/coreclr,yizhang82/coreclr,ruben-ayrapetyan/coreclr,mmitche/coreclr,mmitche/coreclr,rartemev/coreclr,kyulee1/coreclr,kyulee1/coreclr,krk/coreclr,parjong/coreclr,cshung/coreclr,parjong/coreclr,kyulee1/coreclr