Support all path mappings that end in "*" in completions (#21072)

* Support all path mappings that end in "*" in completions

* Check for uppercase TsConfig.JSON

tests/cases/fourslash/completionsPaths_pathMapping.ts

@@ -0,0 +1,19 @@
+/// <reference path="fourslash.ts" />
+
+// @Filename: /src/b.ts
+////export const x = 0;
+
+// @Filename: /src/a.ts
+////import {} from "foo//**/";
+
+// @Filename: /tsconfig.json
+////{
+////    "compilerOptions": {
+////        "baseUrl": ".",
+////        "paths": {
+////            "foo/*": ["src/*"]
+////        }
+////    }
+////}
+
+verify.completionsAt("", ["a", "b"]);