[clang] [Clang] Eagerly instantiate used constexpr function upon definition. (PR #73463)

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cor3ntin wrote:

@zygoloid It took me a while, but I think I got it; what do you think of direction ? (description in the last commit message)
It appears I am doing something a bit novel, but I couldn't think of a better way.

https://github.com/llvm/llvm-project/pull/73463