Updated `newMemorySizer()` to return the updated value, but also
ensure that an invalid `max` still throws an error (invalid module).
- Minor cleanup to use the `memorySizer` type instead of the full
func signature for clarity
- Added a wat+wasm under `internal/integration_test/vs/testdata/`
simply because that's where the other cache-related testdata was.
Closes#1153.
Signed-off-by: Edoardo Vacchi <evacchi@users.noreply.github.com>