Anyone who’s heard Rumer’s 2015 collection B-Sides and Rarities knows that the artist’s leftovers bear the same hallmarks of quality, beauty, emotion, and elegance as her core releases.  Now, seven years later, a second volume is on the way from Cooking Vinyl.  B-Sides and Rarities Vol. 2 arrives April 22 on CD and digitally with a vinyl LP edition to follow from the label on October 21. Since that initial collection, the Pakistani-born British artist has released two studio albums, one EP, and a live release.  The second volume of B-Sides and…