Revisit the comparison view between base and new commit

[huydhn]

Two questions to cover:

• The option we are using atm is to default the base commit to the oldest commit and the new commit to the latest commit in the selected window. There are cases where it's desirable to set both base and new commit to the latest commit Filter out devices that are not run #6277 (comment). We probably want to debate more on which is more useful as the default.
• If there is no overlapping between the base and new commit, for example, one running CPU, the other running GPU benchmark. Or one running Android, the other running iOS. Should we show nothing, or should we show the results from the new commit (the current behavior)

cc @yangw-dev