all: replace target=wasi with target=wasip1

This eliminates the 'wasi' build tag in favor of 'GOOS=wasip1', introduced in Go 1.21.

For backwards compatablity, -target=wasi is a synonym for -target=wasip1.

targets/wasi.json

@@ -1,26 +0,0 @@
-{
-	"llvm-target":   "wasm32-unknown-wasi",
-	"cpu":           "generic",
-	"features":      "+bulk-memory,+mutable-globals,+nontrapping-fptoint,+sign-ext",
-	"build-tags":    ["tinygo.wasm", "wasi"],
-	"goos":          "linux",
-	"goarch":        "arm",
-	"linker":        "wasm-ld",
-	"libc":          "wasi-libc",
-	"rtlib":         "compiler-rt",
-	"scheduler":     "asyncify",
-	"default-stack-size": 65536,
-	"cflags": [
-		"-mbulk-memory",
-		"-mnontrapping-fptoint",
-		"-msign-ext"
-	],
-	"ldflags": [
-		"--stack-first",
-		"--no-demangle"
-	],
-	"extra-files": [
-		"src/runtime/asm_tinygowasm.S"
-	],
-	"emulator":      "wasmtime --dir={tmpDir}::/tmp {}"
-}