[MLIR][GPU] Update serializeToObject to use SerializedObject wrapper and include ISA compiler logs (#176697)
This PR makes the compilation log from ISA compiler available to users
by returning it as part of the `gpu::ObjectAttr` properties, following
the existing pattern like `LLVMIRToISATimeInMs`.
Currently, the compiler log (which contains useful information such as
spill statistics when --verbose is passed) is only accessible in debug
builds via `LLVM_DEBUG`. However, there are good reasons to make this
information available in release builds as well:
1. Both `ptxas` and `libnvptxcompiler` are publicly available
tools/libraries distributed with the CUDA Toolkit. The `--verbose` flag
and its output are documented public features, not internal debug
information.
2. The verbose output provides valuable insights for users.
A new `SerializedObject` class is used to carry the metadata alongside
the binary when returning from `serializeObject`.