[clang-format] New BreakInheritanceList style AfterComma

This inheritance list style has been widely adopted by Symantec,
a division of Broadcom Inc. It breaks after the commas that
separate the base-specifiers:

    class Derived : public Base1,
                    private Base2
    {
    };

Differential Revision: https://reviews.llvm.org/D103204