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

.gitignore

@@ -4,6 +4,10 @@
 /.idea
 **/cmake-build-*/
 **/*build/
+*.obj
+*.a
+*.so
+
 core/deps/**
 core/shared/mem-alloc/tlsf
 core/app-framework/wgl
@@ -12,6 +16,9 @@ wamr-sdk/out/
 wamr-sdk/runtime/build_runtime_sdk/
 test-tools/host-tool/bin/
 product-mini/app-samples/hello-world/test.wasm
+product-mini/platforms/linux-sgx/enclave-sample/App/
+product-mini/platforms/linux-sgx/enclave-sample/Enclave/
+product-mini/platforms/linux-sgx/enclave-sample/iwasm
 
 build_out
 tests/wamr-test-suites/workspace