[clang-format] Preserve trailing NOLINTEND placement with SeparateDefinitionBlocks (#190741)

Fixes https://github.com/llvm/llvm-project/issues/189384.

When `SeparateDefinitionBlocks: Always` is enabled, clang-format may
separate a clearly trailing comment block by inserting an empty line
before it.

For example, it may format:

```c++
// NOLINTBEGIN
int x = 1;
int y = 2;
// NOLINTEND

void some_function() {}
```

as

```c++
// NOLINTBEGIN
int x = 1;
int y = 2;

// NOLINTEND

void some_function() {}
```

This is undesirable as the trailing comment is visually attached to the
preceding block rather than acting as a separator for the following
definition.

This change preserves comment blocks that are clearly trailing the
preceding block.

Also add a regression test.

---------

Co-authored-by: owenca <owenpiano@gmail.com>