clang-format: update latest spec and reformat with clang-21

Copy the latest format file from the docs repository and apply using
clang-format-21.

See I795e88ada8e676c242b5a18888ce9c08afdedc93 for clang-21 enablement.

Change-Id: I08e1dad55a6dd1bc6b56fc47d2ddef7c9bbebdd7
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>