[gsoc2024][libc][math][c23] Implement _Float16 basic operations

[overmighty]

This issue is part of the following Google Summer of Code 2024 project: https://summerofcode.withgoogle.com/programs/2024/projects/1vPVUj93.

• [x] ceilf16: #94001
• [x] canonicalizef16: #94341
• [x] copysignf16: #94351
• [x] fabsf16: #93567
• [x] fdimf16: #94354
• [x] floorf16: #94001
• [x] fmaxf16: #94131
• [x] fmaximumf16: #94510
• [x] fmaximum_magf16: #94510
• [x] fmaximum_mag_numf16: #94510
• [x] fmaximum_numf16: #94510
• [x] fminf16: #94131
• [x] fminimumf16: #94510
• [x] fminimum_magf16: #94510
• [x] fminimum_mag_numf16: #94510
• [x] fminimum_numf16: #94510
• [x] fmodf16: #94629
• [x] frexpf16: #94758
• [x] fromfpf16: #94254
• [x] fromfpxf16: #94254
• [x] ilogbf16: #94758
• [x] ldexpf16: #94797
• [x] llogbf16: #94758
• [x] llrintf16: #94218
• [x] llroundf16: #94218
• [x] logbf16: #94758
• [x] lrintf16: #94218
• [x] lroundf16: #94218
• [x] modff16: #94758
• [x] nanf16: #94767
• [x] nearbyintf16: #94218
• [x] nextafterf16: #94535
• [x] nextdownf16: #94535
• [x] nexttowardf16: #94535
• [x] nextupf16: #94535
• [x] remainderf16: #94773
• [x] remquof16: #94773
• [x] rintf16: #94218
• [x] roundf16: #94001
• [x] roundevenf16: #94001
• [x] scalbnf16: #94797
• [x] scalblnf16: #94797
• [x] truncf16: #94001
• [x] ufromfpf16: #94254
• [x] ufromfpxf16: #94254
• [x] totalorderf16: #95014
• [x] totalordermagf16: #95014
• [x] getpayloadf16: #95159
• [x] setpayloadf16: #95159
• [x] setpayloadsigf16: #95159
• [x] f16add (extension): #97072
• [x] f16addf (extension): #96787
• [x] f16addl (extension): #97072
• [x] f16addf128: #97072
• [x] f16sub (extension): #97072
• [x] f16subf (extension): #96787
• [x] f16subl (extension): #97072
• [x] f16subf128: #97072
• [ ] f16mul (extension): #98972
• [ ] f16mulf (extension): #98972
• [ ] f16mull (extension): #98972
• [ ] f16mulf128: #98972
• [x] f16div (extension): #97054
• [x] f16divf (extension): #96131
• [x] f16divl (extension): #97054
• [x] f16divf128: #97054
• [x] f16fma (extension): #96711
• [x] f16fmaf (extension): #95483
• [x] f16fmal (extension): #96711
• [x] f16fmaf128: #96711

[JonChesterfield]

I think this broke the aarch64 libc bot, e.g. https://lab.llvm.org/buildbot/#/builders/138

[overmighty]

@JonChesterfield See https://github.com/llvm/llvm-project/pull/94569.