Allow missing imports in wasm loader and report error in wasm instantiation instead (#3539)

The wasm loader is failing when multi-module support is on and the dependent
modules are not found; this enforces the AOT compiler integrations to prepare
dependent modules while it isn't necessary.

This PR allows allows missing imports in wasm loader and report error in wasm
instantiation instead, which enables the integrated AOT compiler to work as if
the multi-module support isn't turned on.

tests/wamr-test-suites/spec-test-script/ignore_cases.patch

@@ -43,26 +43,28 @@ index b1e1239..a0f6967 100644
  
  
 diff --git a/test/core/elem.wast b/test/core/elem.wast
-index 33b3f67..c72431c 100644
+index 33b3f67..a4c1a2d 100644
 --- a/test/core/elem.wast
 +++ b/test/core/elem.wast
-@@ -595,9 +595,11 @@
-   (func $const-i32-d (type $out-i32) (i32.const 68))
- )
+@@ -586,6 +586,7 @@
+ (assert_return (invoke $module1 "call-8") (i32.const 65))
+ (assert_return (invoke $module1 "call-9") (i32.const 66))
  
 +(;
+ (module $module2
+   (type $out-i32 (func (result i32)))
+   (import "module1" "shared-table" (table 10 funcref))
+@@ -598,7 +599,9 @@
  (assert_return (invoke $module1 "call-7") (i32.const 67))
  (assert_return (invoke $module1 "call-8") (i32.const 68))
  (assert_return (invoke $module1 "call-9") (i32.const 66))
 +;)
  
++(;
  (module $module3
    (type $out-i32 (func (result i32)))
-@@ -608,9 +610,11 @@
-   (func $const-i32-f (type $out-i32) (i32.const 70))
- )
- 
-+(;
+   (import "module1" "shared-table" (table 10 funcref))
+@@ -611,6 +614,7 @@
  (assert_return (invoke $module1 "call-7") (i32.const 67))
  (assert_return (invoke $module1 "call-8") (i32.const 69))
  (assert_return (invoke $module1 "call-9") (i32.const 70))
@@ -95,7 +97,6 @@ index 33b3f67..c72431c 100644
  
  (assert_return (invoke "call_imported_elem") (i32.const 42))
 +;)
-\ No newline at end of file
 diff --git a/test/core/if.wast b/test/core/if.wast
 index 2ea45f6..6f07304 100644
 --- a/test/core/if.wast