Update merge request widget state actions

What does this MR do and why?

Updates the merge request widget state actions button match the new framework.

For all states, except merge blocked states, the action buttons are now tertiary confirm variant and right aligned. For the merge blocked states the buttons are now confirm variant with the most important being primary and if there is another button it is secondary.

On mobile - the action buttons move into a dropdown. Except for the merge blocked actions these actions wrap underneath the text.

Screenshots or screen recordings

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Numbered steps to set up and validate the change are strongly suggested.

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Closes #368037 (closed)