[BUG] case_insensitive wildcard query didn't return expected result

[HUSTERGS]

Describe the bug

When perform wildcard query on wildcard field with case_insensitive set to true, the expected doc didn't occur.

Related component

Search

To Reproduce

1. Create a simple index contains wildcard field

   PUT case_test
   {
       "mappings": {
           "properties": {
               "wildcard": {
                   "type": "wildcard"
               }
           }
       }
   }
   

2. Bulk insert documents contains capital letters

   PUT _bulk?refresh=true
   {"index": {"_index": "case_test"}}
   {"wildcard": "TtAa"}
   {"index": {"_index": "case_test"}}
   {"wildcard": "ttaa"}
   {"index": {"_index": "case_test"}}
   {"wildcard": "TTAA"}
   

3. Search on wildcard field with case_insensitive set to true and false respectly
   case sensitive:

   POST case_test/_search
   {
       "query": {
           "term": {
               "wildcard": {
                   "value": "TtAa",
                   "case_insensitive": false
               }
           }
       }
   }
   

   case insensitive:

   POST case_test/_search
   {
       "query": {
           "term": {
               "wildcard": {
                   "value": "TtAa",
                   "case_insensitive": true
               }
           }
       }
   }
   

4. Check result

Expected behavior

case insensitive query should return all three documents, instead of TtAa alone

Additional Details

Plugins
Please list all plugins currently enabled.

Screenshots
If applicable, add screenshots to help explain your problem.

Host/Environment (please complete the following information):

• OS: [e.g. iOS]
• Version [e.g. 22]

Additional context
Add any other context about the problem here.

[HUSTERGS]

bugfix is here #15882