Handle allocation errors in UI layer

[martinfouilleul]

Imported from gitea. See https://git.handmade.network/hmn/orca/issues/155 for previous conversation

UI currently calls arena functions without checking the result. It is reasonable to expect that 1MB of memory is enough for most cases but it would be nice to explicitly log an error and crash. This behavior should also be documented - in Zig arena allocation can return explicit errors, and UI functions don't expose errors which can make the user think it can't fail. API-wise, the UI code is better off without error propagation (except on init), it just needs to fail fast and document that it'll do so.

This came out of #154