[clang] [clang-format] Add KeepEmptyLines.AtEndOfBlock option (PR #224223)

[Björn Schäpers via cfe-commits]

================
@@ -25609,6 +25611,51 @@ TEST_F(FormatTest, KeepEmptyLinesAtEOF) {
   verifyFormat(Code, "int i;\n\n\n", Style);
 }
 
+TEST_F(FormatTest, KeepEmptyLinesAtStartOfBlock) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AllowShortFunctionsOnASingleLine =
+      FormatStyle::ShortFunctionStyle::setEmptyAndInline();
+  Style.KeepEmptyLines.AtStartOfBlock = true;
+  Style.MaxEmptyLinesToKeep = 2;
+
+  verifyFormat("void foo() {\n"
+               "\n\n"
----------------
HazardyKnusperkeks wrote:

```suggestion
               "\n"
               "\n"
```
Break each line in the test code, it's easier to read.

https://github.com/llvm/llvm-project/pull/224223