[clang][DeclPrinter] Fix missing semicolon in AST print for methods that are...

[clang][DeclPrinter] Fix missing semicolon in AST print for methods that are definitions without having a body

DeclPrinter used FunctionDecl::isThisDeclarationADefinition to decide if the decl requires a semicolon at the end. However, there are several methods without body (that require a semicolon) that are definitions.

Fixes https://github.com/llvm/llvm-project/issues/62996

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D156533