Add WASI ABI compatibility check for multi-module (#913)

Refer to https://github.com/WebAssembly/WASI/blob/main/design/application-abi.md
to check the WASI ABI compatibility:
- Command (main module) may export _start function with signature "()"
- Reactor (sub module) may export _initialize function with signature "()"
- _start and _initialize can not be exported at the same time
- Reactor cannot export _start function
- Command and Reactor must export memory

And
- Rename module->is_wasi_module to module->import_wasi_api
- Refactor wasm_loader_find_export()
- Remove MULTI_MODULE related codes from mini_loader
- Update multi-module samples
- Fix a "use-after-free" issue. Since we reuse the memory instance of sub module,
   just to protect it from freeing an imported memory instance

samples/multi-module/wasm-apps/mC.c

@@ -1,25 +1,51 @@
+#include <stdio.h>
+#include <stdlib.h>
+
 __attribute__((import_module("mA")))
-__attribute__((import_name("A"))) extern int
-A();
+__attribute__((import_name("A1"))) extern int
+A1();
 
 __attribute__((import_module("mB")))
-__attribute__((import_name("B"))) extern int
-B();
+__attribute__((import_name("B1"))) extern int
+B1();
 
-int
-C()
+__attribute__((import_module("mB")))
+__attribute__((import_name("B2"))) extern int
+B2();
+
+__attribute__((export_name("C1"))) int
+C1()
 {
-    return 12;
+    return 31;
+}
+
+__attribute__((export_name("C2"))) int
+C2()
+{
+    return B1();
+}
+
+__attribute__((export_name("C3"))) int
+C3()
+{
+    return A1();
+}
+
+__attribute__((export_name("C4"))) int
+C4()
+{
+    return B2();
 }
 
 int
-call_A()
+C5()
 {
-    return A();
+    return C1() + C2() + C3() + 35;
 }
 
 int
-call_B()
+main()
 {
-    return B();
+    printf("%u\n", C5());
+    return EXIT_SUCCESS;
 }