Enable AllowShortIfStatementsOnASingleLine in clang-format

Depends: #3708 (closed) (clang-format version)

In !933 (merged), Roland proposed, and Szilárd and Andrey supported the idea of enabling the AllowShortIfStatementsOnASingleLine clang-format option.

We already have AllowShortBlocksOnASingleLine and AllowShortCaseLabelsOnASingleLine enabled.