[libc] Add differential and performance targets for sqrtf

Comparing the runtime of the sqrt functions from LLVM libc with the system libc:
|function       |perf - LLVM libc          |perf - MSVCRT
|sqrtf - Windows|44.05 sec (44051715500 ns)| 417.84 sec (417843359900 ns) = 6.96 mins

|function       |perf - LLVM libc          |perf - glibc
|sqrtf - Linux  |30.48 sec (30479458632 ns)|43.72 sec (43716901527 ns)

By running the differential test:
|function       |diff
|sqrtf - Windows|0 differing results
|sqrtf - Linux  |0 differing results

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D107229