[llvm] [MC][COFF][AArch64] Add helper symbols for large SECREL addends (PR #199602)

[via llvm-commits]

hotschmoe wrote:

i went with "only when needed" and updated PR assuming https://github.com/llvm/llvm-project/pull/200060 gets merged
let me know, thanks!

https://github.com/llvm/llvm-project/pull/199602