[clang-format] add regression tests for braced lists

[krasimir]

Summary

Depends on https://reviews.llvm.org/D116000.

Added test cases from the comments on https://reviews.llvm.org/D114583.

[MyDeveloperDay]

LGTM

[MyDeveloperDay]

thanks for picking this one up (and finding it in the first place)

clang/unittests/Format/FormatTest.cpp

verifyFormat("class C : public D {\n"
                "  SomeClass SC{2};\n"
                "};");
   verifyFormat("class C : public A {\n"
                "  class D : public B {\n"
                "    void f() { int i{2}; }\n"
                "  };\n"
                "};");
   verifyFormat("#define A {a, a},");
+  // Don't confuse braced list initializers with compound statements.
+  verifyFormat(
+      "class A {\n"
+      "  A() : a{} {}\n"
+      "  A(int b) : b(b) {}\n"
+      "  A(int a, int b) : a(a), bs{{bs...}} { f(); }\n"
+      "  int a, b;\n"
+      "  explicit Expr(const Scalar<Result> &x) : u{Constant<Result>{x}} {}\n"
+      "  explicit Expr(Scalar<Result> &&x) : u{Constant<Result>{std::move(x)}} "
+      "{}\n"
+      "};");
 
   // Avoid breaking between equal sign and opening brace
   FormatStyle AvoidBreakingFirstArgument = getLLVMStyle();
   AvoidBreakingFirstArgument.PenaltyBreakBeforeFirstCallParameter = 200;
   verifyFormat("const std::unordered_map<std::string, int> MyHashTable =\n"
                "    {{\"aaaaaaaaaaaaaaaaaaaaa\", 0},\n"
                "     {\"bbbbbbbbbbbbbbbbbbbbb\", 1},\n"
                "     {\"ccccccccccccccccccccc\", 2}};",