(WIP) Enable instantiation from globals

[felipemello1]

Context

What is the purpose of this PR? Is it to

• add a new feature
• fix a bug
• update tests and/or documentation
• other (please add here)

Before this PR, you couldn't instantiate 'my_local_function', .e.g. in a script or a jupyter notebook. We only supported functions that were importable. Now you can do this

def my_local_function():
    return 0
config = {"foo": "_component_": "my_local_function"}
foo = instantiate(config)

TODO: need to test it in notebooks.

Test plan

• Unit test
• Ran a recipe

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/torchtune/2518

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❌ 3 New Failures, 3 Cancelled Jobs

As of commit 2e7e122 with merge base 1241231 ():

NEW FAILURES - The following jobs have failed:

• GPU tests / gpu_test (3.11, stable) (gh)
  tests/torchtune/config/test_config_utils.py::TestUtils::test_get_component_from_path
• Unit Test / unit_tests (3.10) (gh)
  tests/torchtune/config/test_config_utils.py::TestUtils::test_get_component_from_path
• Unit Test / unit_tests (3.11) (gh)
  tests/torchtune/config/test_config_utils.py::TestUtils::test_get_component_from_path

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• GPU tests / gpu_test (3.10, stable) (gh)
  tests/torchtune/config/test_config_utils.py::TestUtils::test_get_component_from_path
• GPU tests / gpu_test (3.9, stable) (gh)
  tests/torchtune/config/test_config_utils.py::TestUtils::test_get_component_from_path
• Unit Test / unit_tests (3.9) (gh)
  ##[error]The operation was canceled.

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[felipemello1]

todo: fix this