[SYCL][ESIMD][EMU] Enable fp64/double type support (intel#6796)

* For PI_DEVICE_INFO_EXTENSIONS, 'piDeviceGetInfo' returns 'cl_khr_fp64'
as the type can be supported as native 'double' type
* Fixes current pre-commit issue with unexpected pass on SYCL :: spec_const/spec_const_double.cpp

Author: dongkyunahn-intel

sycl/plugins/esimd_emulator/pi_esimd_emulator.cpp

@@ -625,7 +625,7 @@ pi_result piDeviceGetInfo(pi_device Device, pi_device_info ParamName,
     // TODO : Populate return string accordingly - e.g. cl_khr_fp16,
     // cl_khr_fp64, cl_khr_int64_base_atomics,
     // cl_khr_int64_extended_atomics
-    return ReturnValue("");
+    return ReturnValue("cl_khr_fp64");
   case PI_DEVICE_INFO_VERSION:
     return ReturnValue(Device->VersionStr.c_str());
   case PI_DEVICE_INFO_BUILD_ON_SUBDEVICE: // emulator doesn't support partition