update doc links to 0.2 version

Summary: In alpha doc, some links are pointing to stable or main branch pytorch documentations. However, for alpha release, we need to make sure those links are also pointing to alpha version. This diff makes the update.

Differential Revision: D56405850

:link: Helpful Links

:test_tube: See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/3205

• :page_facing_up: Preview Python docs built from this PR

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

:x: 3 New Failures

As of commit 3b10bc580b1aae9e12509dfcc51e5554c1d32b09 with merge base 8dc54d569a436b0a02807b5a0dd457f016bd92ce ():

NEW FAILURES - The following jobs have failed:

• Android / test-llama-app / mobile-job (android) (gh) Credentials could not be loaded, please check your action inputs: Could not load credentials from any providers
• Apple / upload-frameworks-ios (gh) Credentials could not be loaded, please check your action inputs: Could not load credentials from any providers
• pull / unittest / linux (buck2) / linux-job (gh) RuntimeError: Command docker exec -t 3ff2d641bb8842c16026c1c4673dc5739c7c679c0904fdc141d68bfa712594e2 /exec failed with exit code 1

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