[clang-format] Don't indent Verilog `begin` keyword on its own line

[sstwcw]

Summary

When the line is too long and the begin keyword wraps to the next
line, it shouldn't be indented.

clang/lib/Format/ContinuationIndenter.cpp

unsigned ContinuationIndenter::getNewLineColumn(const LineState &State) {
   // thus are on the same line as the current token.
   if ((Style.isVerilog() && Keywords.isVerilogEndOfLabel(Previous)) ||
       (Style.BreakBeforeBraces == FormatStyle::BS_Whitesmiths &&
        State.Line->First->is(tok::kw_enum))) {
     return (Style.IndentWidth * State.Line->First->IndentLevel) +
            Style.IndentWidth;
   }
 
-  if (NextNonComment->is(tok::l_brace) && NextNonComment->is(BK_Block)) {
+  if ((NextNonComment->is(tok::l_brace) && NextNonComment->is(BK_Block)) ||
+      (Style.isVerilog() && Keywords.isVerilogBegin(*NextNonComment))) {
     if (Current.NestingLevel == 0 ||
         (Style.LambdaBodyIndentation == FormatStyle::LBI_OuterScope &&
          State.NextToken->is(TT_LambdaLBrace))) {
       return State.FirstIndent;
     }
     return CurrentState.Indent;
   }
   if ((Current.isOneOf(tok::r_brace, tok::r_square) ||

clang/unittests/Format/FormatTestVerilog.cpp

verifyFormat("begin\n"
                "  begin : x\n"
                "  end : x\n"
                "end");
   // Test that 'disable fork' and 'rand join' don't get mistaken as blocks.
   verifyFormat("disable fork;\n"
                "x = x;");
   verifyFormat("rand join x x;\n"
                "x = x;");
+  // The begin keyword should not be indented if it is too long to fit on the
+  // same line.
+  verifyFormat("while (true) //\n"
+               "begin\n"
+               "  while (true) //\n"
+               "  begin\n"
+               "  end\n"
+               "end");
+  verifyFormat("while (true) //\n"
+               "begin : x\n"
+               "  while (true) //\n"
+               "  begin : x\n"
+               "  end : x\n"
+               "end : x");
+  verifyFormat("while (true) //\n"
+               "fork\n"
+               "  while (true) //\n"
+               "  fork\n"
+               "  join\n"
+               "join");
+  auto Style = getDefaultStyle();
+  Style.ColumnLimit = 17;
+  verifyFormat("while (true)\n"
+               "begin\n"
+               "  while (true)\n"
+               "  begin\n"
+               "  end\n"
+               "end",
+               "while (true) begin\n"
+               "  while (true) begin"
+               "  end\n"
+               "end",
+               Style);
 }
 
 TEST_F(FormatTestVerilog, Case) {
   verifyFormat("case (data)\n"
                "endcase");
   verifyFormat("casex (data)\n"
                "endcase");
   verifyFormat("casez (data)\n"