[Executorch] Introduce caching cpu memory allocator

[pytorchbot]

This PR was created by the merge bot to help merge the original PR into the main branch.
ghstack PR number: #15611 by @kimishpatel
^ 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/kimishpatel/203/base
ghstack PR head: https://github.com/pytorch/executorch/tree/gh/kimishpatel/203/head
Merge bot PR base: https://github.com/pytorch/executorch/tree/gh/kimishpatel/202/orig
Merge bot PR head: https://github.com/pytorch/executorch/tree/gh/kimishpatel/203/orig
Differential Revision: D85532079
@diff-train-skip-merge

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⏳ 4 Pending, 1 Unrelated Failure

As of commit 8b88a23 with merge base 4aaa7ff ():

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

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

• pull / android / run-emulator (gh) (trunk failure)
  Timeout waiting for emulator to boot.

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