[NFC] Use `https` instead of `http` in the `LLVM.org` URLs

[philnik]

Could you do this on a per-project basis? More than 1000 files is way to much to sift through.

[efriedma]

A couple notes skimming the changes:

1. If you're going to update URLs, please verify the new URLs are actually valid.
2. Some of the "URLs" you're updating aren't actually URLs. For example, the xmlns attribute in SVG files must be the exact string written in the standard; changing it could make the file unreadable.

[sunshaoce]

Change to only modify *.llvm.org

[JDevlieghere]

+1 on breaking this down per sub-project and creating separate patches for review.

I sampled the patch and about a quarter or so of the links I tried didn't work, even before the change. There's no point in generating churn by changing those, but there's also little value in keeping them around, and fixing them is beyond the scope of this patch. I'm inclined to say let's leave them be, but I'm curious to hear what others think about that.

[sunshaoce]

Thanks for comments!