Move third-party/glob_defs.bzl to shim_et (#9140)

Summary:As titled. Doing this so that `glob_defs.bzl` can be used by
other TARGETS files outside of `third-party/`.

Test Plan: Rely on CI jobs

Reviewers: myuan

Subscribers:

Tasks:

Tags:

### Summary
[PLEASE REMOVE] See [CONTRIBUTING.md's Pull
Requests](https://github.com/pytorch/executorch/blob/main/CONTRIBUTING.md#pull-requests)
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### Test plan
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commands you used and note down tests that you have written if
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