[SYCL] Implement kernel_bundle::get_kernel function (#8294)

`kernel_bundle` was missing the `template <typename KernelName> kernel
get_kernel() const;` from its complete list of queries from the spec
[4.11.12.1](https://registry.khronos.org/SYCL/specs/sycl-2020/html/sycl-2020.html#sec:bundles.query).
This patch implements this missing function.

An E2E test was required in order to test this, the test for this patch
is intel/llvm-test-suite#1589.

Author: Andrew Lamzed-Short

sycl/include/sycl/kernel_bundle.hpp

@@ -276,6 +276,14 @@ class kernel_bundle : public detail::kernel_bundle_plain,
     return detail::kernel_bundle_plain::get_kernel(KernelID);
   }
 
+  /// \returns a kernel object which represents the kernel identified by
+  /// KernelName.
+  template <typename KernelName, bundle_state _State = State,
+            typename = detail::enable_if_t<_State == bundle_state::executable>>
+  kernel get_kernel() const {
+    return detail::kernel_bundle_plain::get_kernel(get_kernel_id<KernelName>());
+  }
+
   /// \returns true if any device image in the kernel_bundle uses specialization
   /// constant whose address is SpecName
   template <auto &SpecName> bool has_specialization_constant() const noexcept {