Add SeparateDefinitionBlocks key to ClangFormat configuration

The previous ClangFormat configuration was developed for use with ClangFormat 11.0.1. The version of ClangFormat now in
use by Arduino tools is 14.0.0.

This configuration key was added in the interim.

The key value set here was chosen in order to:

- Align with behavior of the Arduino IDE 1.x "Auto Format" feature.

The `Leave` value the most permissive.

Author: per1234

other/clang-format-configuration/.clang-format

@@ -135,6 +135,7 @@ QualifierAlignment: Leave
 ReferenceAlignment: Pointer
 ReflowComments: false
 RemoveBracesLLVM: false
+SeparateDefinitionBlocks: Leave
 SortIncludes: Never
 SortUsingDeclarations: false
 SpaceAfterCStyleCast: false