Fix/pagination double fire

[baadhira]

Closes #20995

Fixes a bug where the cds-pagination-changed-current event was firing twice on a single page change.

Changelog

New

• {{new thing}}

Changed

• Refactored the updated lifecycle method in CDSPagination to manually synchronize internal state (start) and UI state (pagesSelect.value) without re-triggering the user-initiated change event.

Removed

• Removed the redundant call to _handleUserInitiatedChangeStart inside the updated lifecycle when the page property changes.

Testing / Reviewing

• Open the Pagination component in Storybook (Web Components).
• Go to the Actions panel at the bottom.
• Click the Next or Previous arrow icons once.
• Verification: Observe that cds-pagination-changed-current is logged exactly once.
• Change the page using the dropdown menu.
• Verification: Observe the event is logged exactly once and the UI remains in sync.
• Run unit tests: yarn test --path components/pagination (Verified: 815 passed).

PR Checklist

As the author of this PR, before marking ready for review, confirm you:

• ] Reviewed every line of the diff
• Updated documentation and storybook examples
• Wrote passing tests that cover this change
• Addressed any impact on accessibility (a11y)
• Tested for cross-browser consistency
• Validated that this code is ready for review and status checks should pass

More details can be found in the pull request guide

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