[clang] [llvm] [BPF] rename 'arena' to 'address_space' (PR #85161)

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eddyz87 wrote:

I also tested this change using [this](https://gist.github.com/eddyz87/1921247819138a9ed70d77db40db8a7c) kernel patch and arena tests are passing.

https://github.com/llvm/llvm-project/pull/85161