[HLSL] Add acos library function

[bob80905]

Summary

This change exposes the acos library function for HLSL scalar types,excluding long long doubles. Acos is supported for all scalar, vector,and matrix types. This patch only adds a subset of scalar type support.

Long long double support is missing in this patch because that type
doesn't exist in HLSL.

The full documentation of the HLSL acos function is available here:
https://docs.microsoft.com/en-us/windows/win32/direct3dhlsl/dx-graphics-hlsl-acos

[bob80905]

remove scalar types lld and ld from test since hlsl won't support them

[beanz]

@bob80905, if you rebase this you should be able to add half support too now. Otherwise this looks good.

clang/lib/Headers/hlsl/hlsl_intrinsics.h

 #define _HLSL_HLSL_INTRINSICS_H_
 
 __attribute__((clang_builtin_alias(__builtin_hlsl_wave_active_count_bits))) uint
 WaveActiveCountBits(bool bBit);
 
 
 __attribute__((clang_builtin_alias(__builtin_acos))) double acos(double In);
 __attribute__((clang_builtin_alias(__builtin_acosf))) float acos(float In);
-__attribute__((clang_builtin_alias(__builtin_acosl))) long double acos(long double In);
-//__attribute__((clang_builtin_alias(__builtin_acosf128))) __float128 acos(__float128 In);
-
 
 
 #endif //_HLSL_HLSL_INTRINSICS_H_

clang/test/CodeGenHLSL/builtins/acos.hlsl

 
 float acos_f(float x)
 {
   return acos(x);
 }
 
 // CHECK: define noundef float @"?acos_f@@YAMM@Z"(
 // CHECK: call noundef float @acosf(float noundef %0)
-
-long double acos_ld(long double x)
-{
-  return acos(x);
-}
-
-// CHECK: define noundef double @"?acos_ld@@YAOO@Z"(
-// CHECK: call noundef double @acosl(double noundef %0)
-
-/*
-long long double acos_lld(long long double x)
-{
-  return acos(x);
-}
-*/