PR #18527: [XLA:CPU][oneDNN] Refactor population of oneDNN post-ops

[copybara-service]

PR #18527: [XLA:CPU][oneDNN] Refactor population of oneDNN post-ops

Imported from GitHub PR #18527

This PR refactors the code that populates post-ops for oneDNN primitive and moves it to onednn_util so that it can be re-used by other primitive kinds in the future.
Copybara import of the project:

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69e22d1 by Akhil Goel akhil.goel@intel.com:

Refactor post-op population

Merging this change closes #18527

FUTURE_COPYBARA_INTEGRATE_REVIEW=#18527 from Intel-tensorflow:akhil/conv_fusions_3_b 69e22d1

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