[clang] [clang] Implement `__builtin_is_implicit_lifetime()` (PR #101807)

[Vlad Serebrennikov via cfe-commits]

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@@ -5637,6 +5638,27 @@ static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
     return false;
   case UTT_IsTriviallyEqualityComparable:
     return isTriviallyEqualityComparableType(Self, T, KeyLoc);
+  case UTT_IsImplicitLifetime: {
+    DiagnoseVLAInCXXTypeTrait(Self, TInfo,
+                              tok::kw___builtin_is_implicit_lifetime);
+    QualType UnqualT = T->getCanonicalTypeUnqualified();
+    if (UnqualT->isScalarType())
----------------
Endilll wrote:

I updated the patch with more tests for FP and extensions. I discovered that vector types are not considered implicit-lifetime, so I made them so. Here are tests I left out, because Clang told me ~~to go away~~ that they are not supported on the target or require special compiler flags (matrix). I took that as going over the board w.r.t. other type traits tests.
```cpp
typedef float m4x4_t __attribute__((matrix_type(4, 4)));

static_assert(__builtin_is_implicit_lifetime(__SVInt8_t));
static_assert(__builtin_is_implicit_lifetime(__rvv_int8mf8_t));
static_assert(__builtin_is_implicit_lifetime(half));
static_assert(__builtin_is_implicit_lifetime(__float128));
static_assert(__builtin_is_implicit_lifetime(__ibm128));
static_assert(__builtin_is_implicit_lifetime(__externref_t));
static_assert(__builtin_is_implicit_lifetime(__externref_t[2]));
static_assert(__builtin_is_implicit_lifetime(m4x4_t));
```
@AaronBallman Let me know if something is surprising to you, or if I forgot anything. 

https://github.com/llvm/llvm-project/pull/101807