[libc] [llvm] [libc][math][c23] Add {,u}fromfp{,x}{,f,l,f128} functions (PR #86003)

[via llvm-commits]

================
@@ -839,6 +839,198 @@ add_fp_unittest(
     libc.src.math.frexpf128
 )
 
+add_fp_unittest(
+  fromfp_test
+  SUITE
+    libc-math-smoke-tests
+  SRCS
+    fromfp_test.cpp
+  HDRS
+    FromfpTest.h
+  DEPENDS
+    libc.src.math.fromfp
----------------
overmighty wrote:

In my previous PR for `nextup` and `nextdown` I had added more dependencies: https://github.com/llvm/llvm-project/pull/85431/files#diff-2269fc16d8717f30b774875846f93f54879dae7515bdfd3dd5d5645fd7413aa7R1626-R1628.

Now that I think about it again, I assume that depending on `libc.src.math.<func>` is enough to also depend on the header and dependencies declared in the `add_entrypoint_object` call for the function in libc/src/math/generic/CMakeLists.txt.

https://github.com/llvm/llvm-project/pull/86003