Define @deprecated and @experimental decorators

[dbort]

Summary:
Define decorators that EXIR can use to annotate non-stable APIs.

I used the name warnings to parallel the new warnings.deprecated decorator from PEP-702.

Also added typing-extensions as an explicit requirement for the pip package. We already use it in other places, but were getting it transitively from the torch package.

Differential Revision: D61367967

[pytorch-bot]

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❌ 1 New Failure, 1 Unrelated Failure

As of commit 97e4b40 with merge base 9a98abb ():

NEW FAILURE - The following job has failed:

• Android / test-llama-app (bpe) / mobile-job (android) (gh)
  Could not assume role with user credentials: User: arn:aws:sts::308535385114:assumed-role/gh-ci-github-action-runners-runner-role/i-083a91c1206ddd32e is not authorized to perform: sts:TagSession on resource: arn:aws:iam::308535385114:role/gha_workflow_mobile_job

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

• Apple / upload-frameworks-ios (gh) (detected as infra flaky with no log or failing log classifier)

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This pull request was exported from Phabricator. Differential Revision: D61367967