executorch [executorch] Migrate exec_aten util tests to new namespace

Stack from ghstack (oldest at bottom):

#4621
#4620
#4619
#4618
#4617
#4616
#4615
#4614
#4613
#4612
#4611
-> #4610
#4609
#4608
#4607
#4606
#4605

The previous commit moved headers to the ::executorch::runtime namespace. This diff updates the tests for those changes. After this, these tests should not use ::torch::executor for the updated names.

Differential Revision: D60532174

Aug 09 '24 00:08 dbort

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/4610

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:x: 1 New Failure, 1 Cancelled Job

As of commit b541d946a226c8ab2314f875b530282645d967dc with merge base 5c9a00a3e34aa008510989febc42f1de90351494 ():

NEW FAILURE - The following job has failed:

Android / test-llama-app (bpe) / mobile-job (android) (gh) Process completed with exit code 1.

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pull (gh)

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