dvc studio login automatically push experiments by default (#10331)

* studio login set auto_push + add logs for the user

* set a separate global config dir for studio login tests

The `isolate` fixture sets a separate, _isolated_ global config directory.
But it is shared among other tests. So any mutations to it affects other
tests too.

We should force `studio login` tests to use a separate tmp_dir for global config.

* cleanup message

---------

Co-authored-by: Saugat Pachhai (सौगात) <[email protected]>

tests/unit/command/test_studio.py

@@ -1,9 +1,18 @@
+import pytest
 from dvc_studio_client.auth import AuthorizationExpiredError
 
+from dvc import env
 from dvc.cli import main
 from dvc.utils.studio import STUDIO_URL
 
 
+@pytest.fixture(autouse=True)
+def global_config_dir(monkeypatch, tmp_dir_factory):
+    monkeypatch.setenv(
+        env.DVC_GLOBAL_CONFIG_DIR, str(tmp_dir_factory.mktemp("studio-login"))
+    )
+
+
 def test_studio_login_token_check_failed(mocker):
     mocker.patch(
         "dvc_studio_client.auth.get_access_token",