Fix first letter matching for method overrides

[hopehadfield]

Fixes #2884, redhat-developer/vscode-java#3186, and redhat-developer/vscode-java#3214.

[rgrunber]

LGTM.

Just a few unrelated things I noticed, you may want to address in a separate PR :

--- old.txt	2023-10-11 18:16:55.284431675 -0400
+++ new.txt	2023-10-11 18:18:12.486804631 -0400
@@ -5,21 +5,21 @@
                 "description": "boolean"
             },
             "kind": 2,
-            "detail": "Override method in 'Visitor'",
-            "sortText": "999999099",
-            "filterText": "visit",
+            "detail": "Visitor.visit(ElemA input, String something) : boolean",
+            "sortText": "999998971",
+            "filterText": "visit(ElemA input, String something) : boolean",
             "insertText": "visit",
             "textEditText": "visit",
             "command": {
                 "title": "",
                 "command": "java.completion.onDidSelect",
                 "arguments": [
-                    "2",
-                    "0"
+                    "9",
+                    "25"
                 ]
             },
             "data": {
-                "pid": "0",
-                "rid": "2"
+                "pid": "25",
+                "rid": "9"
             }
-        }
+        }

The filterText for the method declaration prevents it from being filtered based on parameters. I think we should set it to be the same as method invocations.

Also, I noticed invocation are sorted in reverse order relative to declarations ? Though this may be another long-standing issue.