[llvm] [Support] Add end/error to decode[US]LEB128AndInc (PR #90006)

[Adrian Prantl via llvm-commits]

https://github.com/adrian-prantl commented:

Technically this still lets users do the inherently unsafe endless scan of a non-normalized value 0x8080808080808080808080... that exceeds the size of the buffer. Maybe we should require passing the end of the buffer in?

https://github.com/llvm/llvm-project/pull/90006