[flang][cuda] Allow object with SHARED attribute as definable (#82822)

A semantic error was raised in device subprogram like: 

```
attributes(global) subroutine devsubr2()
   real, shared :: rs
   rs = 1
end subroutine
```

Object with the SHARED attribute can be can be read or written by all
threads in the block.


https://docs.nvidia.com/hpc-sdk/archive/24.1/compilers/cuda-fortran-prog-guide/index.html#cfpg-var-qual-attr-shared

Author: clementval

flang/lib/Semantics/definable.cpp

@@ -160,9 +160,10 @@ static std::optional<parser::Message> WhyNotDefinableBase(parser::CharBlock at,
             "'%s' is a host-associated allocatable and is not definable in a device subprogram"_err_en_US,
             original);
       } else if (*cudaDataAttr != common::CUDADataAttr::Device &&
-          *cudaDataAttr != common::CUDADataAttr::Managed) {
+          *cudaDataAttr != common::CUDADataAttr::Managed &&
+          *cudaDataAttr != common::CUDADataAttr::Shared) {
         return BlameSymbol(at,
-            "'%s' is not device or managed data and is not definable in a device subprogram"_err_en_US,
+            "'%s' is not device or managed or shared data and is not definable in a device subprogram"_err_en_US,
             original);
       }
     } else if (!isOwnedByDeviceCode) {

flang/test/Semantics/cuf03.cuf

@@ -62,4 +62,11 @@ module m
     !ERROR: Object 'rc' with ATTRIBUTES(CONSTANT) may not be declared in a host subprogram
     real, constant :: rc
   end subroutine
+
+  attributes(global) subroutine devsubr2()
+    real, shared :: rs
+
+    rs = 1 ! ok
+  end subroutine
+
 end module