[lld] [lld][ICF] Don't merge symbols with different addends (PR #139493)

[Pranav Kant via llvm-commits]

pranavk wrote:

Original lld commit was reverted. So I have reapplied that commit in this PR and committed changes to fix the problem in a different commit. You can just look at latest commit to see those changes to make review simple.

This commit basically stops section folding when addends are different which would automatically stop symbol folding. Yes, it means that we would be folding less sections now. I am hoping we wouldn't see too much of this pattern. So it's not going to be noticeable regression. One way to fix this would be to only stop section folding when the relocation is non-trivial but as we discussed in #136641, that's most likely going to bring target-specific logic in which we are not sure we want to do. We can continue building consensus on that in that PR while we let this in?

https://github.com/llvm/llvm-project/pull/139493