[FLAX] glue training example refactor (#13815)

* refactor run_flax_glue.py

* updated readme

* rm unused import and args typo fix

* refactor

* make consistent arg name across task

* has_tensorboard check

* argparse -> argument dataclasses

* refactor according to review

* fix

examples/flax/test_examples.py

@@ -85,10 +85,10 @@ class ExamplesTests(TestCasePlus):
             --per_device_train_batch_size=2
             --per_device_eval_batch_size=1
             --learning_rate=1e-4
-            --max_train_steps=10
-            --num_warmup_steps=2
+            --eval_steps=2
+            --warmup_steps=2
             --seed=42
-            --max_length=128
+            --max_seq_length=128
             """.split()
 
         with patch.object(sys, "argv", testargs):