test(eslint-plugin): [no-unused-vars] add export import namespace testcase (typescript-eslint#8552)

Author: yeonjuan

packages/eslint-plugin/tests/rules/no-unused-vars/no-unused-vars.test.ts

@@ -1113,6 +1113,14 @@ export = {} as Foo;
 declare module 'foo' {
   type Foo = 1;
   export = Foo;
+}
+    `,
+    `
+namespace Foo {
+  export const foo = 1;
+}
+export namespace Bar {
+  export import TheFoo = Foo;
 }
     `,
   ],
@@ -1920,5 +1928,27 @@ export = Foo;
         },
       ],
     },
+    {
+      code: `
+namespace Foo {
+  export const foo = 1;
+}
+export namespace Bar {
+  import TheFoo = Foo;
+}
+      `,
+      errors: [
+        {
+          messageId: 'unusedVar',
+          line: 6,
+          column: 10,
+          data: {
+            varName: 'TheFoo',
+            action: 'defined',
+            additional: '',
+          },
+        },
+      ],
+    },
   ],
 });