[ET-VK] Add etvk.use_existing_vma config to avoid duplicate VMA symbols

[pytorchbot]

This PR was created by the merge bot to help merge the original PR into the main branch.
ghstack PR number: #18522 by @SS-JIA
^ Please use this as the source of truth for the PR details, comments, and reviews
ghstack PR base: https://github.com/pytorch/executorch/tree/gh/SS-JIA/512/base
ghstack PR head: https://github.com/pytorch/executorch/tree/gh/SS-JIA/512/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/main
Merge bot PR head: https://github.com/pytorch/executorch/tree/gh/SS-JIA/512/orig
Differential Revision: D98250268
@diff-train-skip-merge

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/18797

• 📄 Preview Python docs built from this PR

Note: Links to docs will display an error until the docs builds have been completed.

❗ 1 Active SEVs

There are 1 currently active SEVs. If your PR is affected, please view them below:

• Rolling out OSDC (ARC) runners on pull workflow for PyTorch trunk commits

❌ 1 New Failure, 2 Pending, 2 Unrelated Failures

As of commit c01686c with merge base 0ee0f67 ():

NEW FAILURE - The following job has failed:

• Cadence Build & Test / cpu-test / test-aot / test-aot (gh)
  backends/cadence/aot/tests/test_replace_ops_passes.py::TestReplaceOpsPasses::test_replace_conv2d_with_linear

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• Test QNN Backend / test-qnn / test-backend-linux (qnn, models) / linux-job (gh) (matched linux rule in flaky-rules.json)
  The process '/usr/bin/git' failed with exit code 128

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / test-samsung-models-linux / linux-job (gh) (trunk failure)
  test_w2l_fp16

This comment was automatically generated by Dr. CI and updates every 15 minutes.

[github-actions]

This PR needs a release notes: label

If your change should be included in the release notes (i.e. would users of this library care about this change?), please use a label starting with release notes:. This helps us keep track and include your important work in the next release notes.

To add a label, you can comment to pytorchbot, for example
@pytorchbot label "release notes: none"

For more information, see
https://github.com/pytorch/pytorch/wiki/PyTorch-AutoLabel-Bot#why-categorize-for-release-notes-and-how-does-it-work.