Implement most missing wasm-c-api APIs (#303) (#676)

Remove unnecessary functions and implement more APIs:
- wasm_##name##same
- wasm##name##as_ref
- wasm_ref_as##name##
- wasm_ref_delete
- wasm_module_validate
- wasm_table_get/set/size
- wasm_memory_size
- wasm_config_new
- wasm_foreign_new

And add more wasm-c-api samples, update the related documen, add more CI rules.

Signed-off-by: Wenyong Huang <wenyong.huang@intel.com>

samples/wasm-c-api/src/hostref.wat

@@ -0,0 +1,24 @@
+(module
+  (import "" "f" (func $fun (param externref) (result externref)))
+
+  (global $glob (export "global") (mut externref) (ref.null extern))
+  (table $tab (export "table") 10 externref)
+
+  (func (export "global.set") (param $r externref)
+    (global.set $glob (local.get $r))
+  )
+  (func (export "global.get") (result externref)
+    (global.get $glob)
+  )
+
+  (func (export "table.set") (param $i i32) (param $r externref)
+    (table.set $tab (local.get $i) (local.get $r))
+  )
+  (func (export "table.get") (param $i i32) (result externref)
+    (table.get $tab (local.get $i))
+  )
+
+  (func (export "func.call") (param $r externref) (result externref)
+    (call $fun (local.get $r))
+  )
+)