[release-branch.go1.21] misc/wasm: switch default WASI runtime

The default WASI runtime was originally set to Wazero, because it was
the first runtime used to test the Go implementation and because we
could easily find and fix issues in our implementation and theirs.

In CL 498675 we switched the default wasip1 runner to Wasmtime as it
runs faster and is a more established and mature runtime. We should
switch the default runtime to Wasmtime to consistently promote
Wasmtime as the primary tested and approved runtime.

Change-Id: Ic6c064142321af90f015e02b7fe0e71444d8842c
Reviewed-on: https://go-review.googlesource.com/c/go/+/513235
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Eli Bendersky <eliben@google.com>
Run-TryBot: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Auto-Submit: Johan Brandhorst-Satzkorn <johan.brandhorst@gmail.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
(cherry picked from commit 4918490)
Reviewed-on: https://go-review.googlesource.com/c/go/+/514155
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: David Chase <drchase@google.com>

misc/wasm/go_wasip1_wasm_exec

@@ -10,12 +10,12 @@ case "$GOWASIRUNTIME" in
 	"wasmer")
 		exec wasmer run --dir=/ --env PWD="$PWD" --env PATH="$PATH" ${GOWASIRUNTIMEARGS:-} "$1" -- "${@:2}"
 		;;
-	"wasmtime")
-		exec wasmtime run --dir=/ --env PWD="$PWD" --env PATH="$PATH" --max-wasm-stack 1048576 ${GOWASIRUNTIMEARGS:-} "$1" -- "${@:2}"
-		;;
-	"wazero" | "")
+	"wazero")
 		exec wazero run -mount /:/ -env-inherit -cachedir "${TMPDIR:-/tmp}"/wazero ${GOWASIRUNTIMEARGS:-} "$1" "${@:2}"
 		;;
+	"wasmtime" | "")
+		exec wasmtime run --dir=/ --env PWD="$PWD" --env PATH="$PATH" --max-wasm-stack 1048576 ${GOWASIRUNTIMEARGS:-} "$1" -- "${@:2}"
+		;;
 	*)
 		echo "Unknown Go WASI runtime specified: $GOWASIRUNTIME"
 		exit 1