[DO] Renaming "Walkthrough" to "Tutorial"

[Oxyjun]

Summary

Currently the "Get started" section for DO is looking a bit messy. We have

• Walkthrough
• Tutorial with SQL API
• Video series

Walkthrough and Tutorial with SQL API are identical with the exception of which backend storage API it uses. This PR unifies the naming convention for consistency.

We may wish to consider a separate PR to position the video series in a different location.

Screenshots (optional)

Documentation checklist

• The documentation style guide has been adhered to.
• If a larger change - such as adding a new page- an issue has been opened in relation to any incorrect or out of date information that this PR fixes.
• Files which have changed name or location have been allocated redirects.

[github-actions]

This PR changes current filenames or deletes current files. Make sure you have redirects set up to cover the following paths:

• /durable-objects/get-started/walkthrough/

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[github-actions]

Files with changes (up to 15)

Original Link	Updated Link
https://developers.cloudflare.com/durable-objects/best-practices/websockets/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/best-practices/websockets/
https://developers.cloudflare.com/durable-objects/examples/alarms-api/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/alarms-api/
https://developers.cloudflare.com/durable-objects/examples/build-a-counter/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/build-a-counter/
https://developers.cloudflare.com/durable-objects/examples/build-a-rate-limiter/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/build-a-rate-limiter/
https://developers.cloudflare.com/durable-objects/examples/durable-object-in-memory-state/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/durable-object-in-memory-state/
https://developers.cloudflare.com/durable-objects/examples/durable-object-ttl/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/durable-object-ttl/
https://developers.cloudflare.com/durable-objects/examples/websocket-hibernation-server/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/websocket-hibernation-server/
https://developers.cloudflare.com/durable-objects/examples/websocket-server/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/examples/websocket-server/
https://developers.cloudflare.com/durable-objects/get-started/tutorial/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/get-started/tutorial/
https://developers.cloudflare.com/durable-objects/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/durable-objects/
https://developers.cloudflare.com/kv/concepts/kv-bindings/	https://jun-do-get-started-name-unif.cloudflare-docs-7ou.pages.dev/kv/concepts/kv-bindings/