cmd/compile: Pow10 freeze the compiler on certain condition on Go 1.24 [1.24 backport]

[gopherbot]

@Jorropo requested issue #71852 to be considered for backport to the next 1.24 minor release.

@gopherbot Please open backport issue for 1.24

This is a regression where non esoteric code that used to build now does not.
https://gophers.slack.com/archives/C6CM8NUEB/p1740060033459149

[Jorropo]

I've submitted two different proper fixes:

• https://go-review.googlesource.com/c/go/+/650975
• https://go-review.googlesource.com/c/go/+/650580

We merged the simple 2 sloc fix.

My original plan to revert 820f58a would not solve all regression cases, just the particular one discovered in #71852.

~~I think the only correct revert would involve reverting most of @randall77's prove constants handling improvements, so I think we should consider backporting the fix altho this is more risky~~ edit: the previous implementation has known bugs that were fixed in this refactor like #67625. I don't think that relevant to bring this up anymore.

If rather than backporting, we could revert 3b96eeb which would be very messy and require reverting more commits than I have fingers.