double size of chunk each time we hit the global allocator for a new chunk

[fitzgen]

Within reason. Should probably have a max chunk size.

[Kerollmops]

Hey, I think I indeed hit the global allocator, bumpalo was trying to allocate 13GiB and the global allocator (jemalloc) refuses to do that, crashing the program. I could have used the try_ methods, but it is not possible when you use certain crates, like hashbrown (with the bumpalo feature).

It could indeed be a good thing to be able to set the maximum size of a chunk. Maybe a method on the Bump type?

[fitzgen]

I think it would make sense to try doubling and if that doesn't succeed, then try the current chunk size again, and if that fails, then call the OOM handler.

If you'd like to make this PR, I would be happy to review it.