cpp-example: Add std::vector example

cpp-example: Add std::vector example

Add a standard container (std::vector) to the C++ example program to
demonstrate the debugger's capability to inspect and traverse STL
containers during a debugging session. This requires enabling GDB's
pretty-printing feature, which depends on Python scripts shipped with
the compiler.

Signed-off-by: Adrian Freihofer <adrian.freihofer@siemens.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Ross Burton <ross.burton@arm.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>