wasm loader: Fix several issues in GC and exception handling

[wenyongh]

Fix several issues of GC and exception handling in wasm loader:

• Should restore param_reftype_maps/param_reftype_map_count/param_count
  in the handling of opcode throw
• Should set wasm_ref_type when pushing param types of tag type and block type
  if the type is a multi-byte type
• Should set init_values.data as NULL for opcode struct.new_default in load_init_expr

This PR fixes the issues reported in #3411.

[xujuntwt95329]

LGTM