The BorrowChecker methods get inlined as part of the GuestMemory trait. The BorrowChecker implementation moves out to the engines. Unfortunately this does mean having a copy in `test-helpers` along with another in `wasmtime-wiggle`. The `wasmtime-wiggle` copy will move into `wasmtime` itself in a subsequent PR. https://github.com/bytecodealliance/wasmtime/issues/1917