iwasm: Disable app heap by default if wasi is enabled (#2346)

It's rare to require app heap with wasi and sometimes harmful in some cases:
https://github.com/bytecodealliance/wasm-micro-runtime/issues/2275

product-mini/platforms/posix/main.c

@@ -465,7 +465,12 @@ main(int argc, char *argv[])
     const char *func_name = NULL;
     uint8 *wasm_file_buf = NULL;
     uint32 wasm_file_size;
-    uint32 stack_size = 64 * 1024, heap_size = 16 * 1024;
+    uint32 stack_size = 64 * 1024;
+#if WASM_ENABLE_LIBC_WASI != 0
+    uint32 heap_size = 0;
+#else
+    uint32 heap_size = 16 * 1024;
+#endif
 #if WASM_ENABLE_FAST_JIT != 0
     uint32 jit_code_cache_size = FAST_JIT_DEFAULT_CODE_CACHE_SIZE;
 #endif

product-mini/platforms/windows/main.c

@@ -243,7 +243,12 @@ main(int argc, char *argv[])
     const char *func_name = NULL;
     uint8 *wasm_file_buf = NULL;
     uint32 wasm_file_size;
-    uint32 stack_size = 64 * 1024, heap_size = 16 * 1024;
+    uint32 stack_size = 64 * 1024;
+#if WASM_ENABLE_LIBC_WASI != 0
+    uint32 heap_size = 0;
+#else
+    uint32 heap_size = 16 * 1024;
+#endif
 #if WASM_ENABLE_JIT != 0
     uint32 llvm_jit_size_level = 3;
     uint32 llvm_jit_opt_level = 3;