Rename branch "Compare" as "Merge preview"

Branch compare option doesn't serve the purpose or it is same as pull request diff.

Example:

• Create conflict between 2 branches by changing few lines in the file
• View the option "Branch Compare". Having the name branch compare, the feature should show the current difference between files on two branches, instead the preview is same as diff/Merge preview

Hence renaming the feature name to merge preview should be considered if exact branch differences are not shown