Last year, it was ­Manhattan. This time, our ­roundtable ­convenes in L.A., where no topic—from diamonds to ­discounts, from sales to ­salespeople—is off-limits for these jewelers and store owners.On a sunny afternoon in early February, I had the privilege of sitting down with eight Los Angeles–based retailers and designers at the Avalon Hotel, a mid-century gem in Beverly Hills, for a candid, two-hour talk about the state of the fine jewelry business. The spirited, thoughtful discussion touched on a range of topics, from holiday 2011 sales, to the lasting lessons of the Great Reces