[clang] [clang-tools-extra] [lld] [lldb] [llvm] [mlir] Rename llvm::ThreadPool -> llvm::DefaultThreadPool (NFC) (PR #83702)

[David Blaikie via cfe-commits]

dwblaikie wrote:

> I did the first part of the renaming @dwblaikie : looks good?

Hmm - this patch still seems to have both renamings in it, if I'm reading the PR correctly? I take it from the subject that isn't the intent/the intent is that his patch only does the ThreadPool->DefaultThreadPool change?

https://github.com/llvm/llvm-project/pull/83702