chores(ci): add new changelog gen workflow

[hoangdv2429]

Description

This PR add auto changelog workflow as the following:

When new commit pushed/PR merged to main branch then

Check if a changelog PR already opened:

• (Yes) merge from main branch (with ort strag) if needed, then new changelog entry will be append to changelog.md and update to already open PR then exit.
• (No) checkout from main branch, generate changelog entry and create PR.

Branch should delete automatically on next ci run, or you can delete it manully.

NOTE

Do not create branch "auto-changelog-update-do-not-create-manually" manually.

All items are required. Please add a note to the item if the item is not applicable and
please add links to any relevant follow-up issues.

PR review checkboxes:

I have...

• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Targeted PR against the correct branch
• included the correct type prefix in the PR title
• Linked to the GitHub issue with discussion and accepted design
• Targets only one GitHub issue
• Wrote unit and integration tests
• Wrote relevant migration scripts if necessary
• All CI checks have passed
• Added relevant godoc comments
• Updated the scripts for local run, e.g genesis_config_commands.sh if the PR changes parameters
• Add an issue in the e2e-tests repo if necessary

SDK Checklist

• Import/Export Genesis
• Registered Invariants
• Registered Events
• Updated openapi.yaml
• No usage of go map
• No usage of time.Now()
• Used fixed point arithmetic and not float arithmetic
• Avoid panicking in Begin/End block as much as possible
• No unexpected math Overflow
• Used sendCoin and not SendCoins
• Out-of-block compute is bounded
• No serialized ID at the end of store keys
• UInt to byte conversion should use BigEndian

Full security checklist here

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For Reviewer:

• Confirmed the correct type prefix in the PR title
• Reviewers assigned
• Confirmed all author checklist items have been addressed

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After reviewer approval:

• In case the PR targets the main branch, PR should not be squash merge in order to keep meaningful git history.
• In case the PR targets a release branch, PR must be rebased.

[hoangdv2429]

github-action doesn't have permission to push here.

[hoangdv2429]

DO NOT MERGE until further commit being merged on dymint to ensure stability