storage: use uint64_t for batch type map

[bashtanov]

We are about to run out of ids. Also, the static assert as it was wouldn't work as it's off by one.

Backports Required

• [x] none - not a bug fix
• [ ] none - this is a backport
• [ ] none - issue does not exist in previous branches
• [ ] none - papercut/not impactful enough to backport
• [ ] v24.1.x
• [ ] v23.3.x
• [ ] v23.2.x

Release Notes

• none