Sepolia x Shapella readiness

Part of #577

According to https://github.com/ethereum/pm/issues/711, Sepolia x Shapella HF is planning to be on **Tuesday, February 28th**. Some TODOs here:

- [ ] **[staking-deposit-cli]** Cut a new release. It will be a release to support all public testnets (ZheJiang/Sepolia/Goerli/Mainnet) settings. Hopefully will happen next week.
- [ ] **[launchpad]** Move `staking-deposit-cli` tutorial content (https://notes.ethereum.org/@launchpad/btec) to the launchpad site
- [ ] **[launchpad]** Port `shapella` updates to `dev`+`master` (#580, #592)

Discussion:
- [ ] Should we change the wording and env vars so that Sepolia and Goerli show different context for now? Or just update both together? Sepolia/Goerli/Mainnet should have EF blog post announcements, so we can just leave a note of "Please wait for the announcements about the hard fork timing".

Anything else?

Start by reviewing the staking-deposit-cli release TODO, the launchpad tutorial at the linked Notes page, and the Shapella updates referenced in #580 and #592. Done means resolving the release, tutorial migration, and branch-porting checklist items, then deciding how Sepolia and Goerli wording and environment variables should differ or be updated together.

Written by the indexing model from the issue text.