[llvm] [llvm-debuginfo-analyzer] Remove `LVScope::Children` container (PR #144750)

[Javier Lopez-Gomez via llvm-commits]

jalopezg-git wrote:

> @jalopezg-git I think the base branch for this patch should be #144744. This patch should have only the changes to the `Children` container.

That is right -- I can probably just rebase it atop `main` once https://github.com/llvm/llvm-project/pull/144744 is landed.  On this side, we are missing the element ordering (that's why some tests fail).
But, the current state should be enough to see what are the memory savings and if it pays off for the additional work :slightly_smiling_face:.  Could you run the tool w/ that big Chrome debug info file again?

https://github.com/llvm/llvm-project/pull/144750