Integrate LLVM to llvm/llvm-project@4641f4879e47 (#24713)

Integrates LLVM from abbcebe652841d to 4641f4879e47

IREE changes:
- Adapted to llvm/llvm-project#209424, which changed
`llvm::OptimizationLevel` from a class to an enum.
- Changed `DispatchCreationOptions` in
compiler/src/iree/compiler/Pipelines/Options.h so that `optLevel` is
explicitly initialized to `llvm::OptimizationLevel::O2`. This was the
default value of the old `llvm::OptimizationLevel` class.
- As a side note `CodegenPipelineOptLevel` in
‎compiler/src/iree/compiler/Codegen/Utils/CodegenOptions.h was intended
as a bridge from the old llvm class. Now, that enum seems to duplicate
the new llvm enum, but I did not remove it.
- Adapted to llvm/llvm-project#204707, which changed
LLVM::FunctionEntryCountAttr while LLVMFuncOp::build in
llvm-project/mlir/lib/Dialect/LLVMIR/IR/LLVMDialect.cpp still expects
`std::optional<uint64_t>`

The integrate caused the following failing tests, that got addressed
with the cherry-picked changes below
```
  The following tests FAILED:
        1750 - iree/tests/e2e/matmul/e2e_matmul_cpu_dt_uk_f16_f16_llvm-cpu_local-task_avx2 (SEGFAULT) cpu_features=avx2 driver=local-task iree/tests/e2e/matmul noriscv nowasm
        1756 - iree/tests/e2e/matmul/e2e_matmul_cpu_dt_uk_bf16_bf16_llvm-cpu_local-task_avx2 (SEGFAULT) cpu_features=avx2 driver=local-task iree/tests/e2e/matmul noriscv nowasm
        1812 - iree/tests/e2e/matmul/e2e_matmul_cpu_experimental_dt_uk_f16_f16_llvm-cpu_local-task_avx2 (SEGFAULT) cpu_features=avx2 driver=local-task iree/tests/e2e/matmul noriscv nowasm
        1818 - iree/tests/e2e/matmul/e2e_matmul_cpu_experimental_dt_uk_bf16_bf16_llvm-cpu_local-task_avx2 (SEGFAULT) cpu_features=avx2 driver=local-task iree/tests/e2e/matmul noriscv nowasm
``` 
Additional LLVM fixups:
- Cherry-picked https://github.com/llvm/llvm-project/pull/210303
- Cherry-picked https://github.com/llvm/llvm-project/pull/209345

---------

Signed-off-by: Juan Pisula <juanigpisula@gmail.com>