Add testnet4 entry in chainparams

[2seaq]

Added an entry in chainparams for testnet4

Changelog-Added: entry in chainparams for testnet4

Important

24.11 FREEZE NOVEMBER 7TH: Non-bugfix PRs not ready by this date will wait for 25.02.

Checklist

Before submitting the PR, ensure the following tasks are completed. If an item is not applicable to your PR, please mark it as checked:

• The changelog has been updated in the relevant commit(s) according to the guidelines.
• Tests have been added or modified to reflect the changes.
• Documentation has been reviewed and updated as needed.
• Related issues have been listed and linked, including any that this PR closes.

[niftynei]

just as a driveby review comment: we don't use merge commits in CLN (your last commit is a merge commit). we use rebases. you'll need to remove that commit before this PR is eligible for being included in the main branch :)

[cdecker]

Rebased on top of master in order to remove the merge commits. I also squashed the two fixups that you had.

[cdecker]

cACK

[cdecker]

Ah, I hate the Update PR button, it defaults to merge commits...

[2seaq]

eek sorry. I should have checked first

[cdecker]

eek sorry. I should have checked first

Don't worry, I was just commenting about my own oversight that I should have selected rebase rather than just smashing the update button :-)

You're doing good 👍

[ShahanaFarooqui]

Re-based and removed merge commit while cherry-picking few commits from duplicate PR #7895.

@cdecker has already approved both PRs, so it should be ready to merge once it passes the CI checks.