testsuite, cp: increase the coverage of testing pass-by-ref arguments

Extend testcases for GDB's infcall of call-by-value functions that
take aggregate values as parameters.  In particular, existing test has
been substantially extended with class definitions whose definitions
of copy constructor, destructor, and move constructor functions are a
combination of

(1) explicitly defined by the user,
(2) defaulted inside the class declaration,
(3) defaulted outside the class declaration,
(4) deleted
(5) not defined in the source.

For each combination, a small and a large class is generated as well
as a derived class and a container class.  Additionally, the following
manually-written cases are provided:

- a dynamic class (i.e. class with a virtual method)
- classes that contain an array field
- a class whose copy ctor is inlined
- a class whose destructor is deleted
- classes with multiple copy and/or move ctors

Test cases check whether GDB makes the right decision to pass an
object by value or implicitly by reference, whether really a copy of
the argument is passed, and whether the copy constructor and
destructor of the clone of the argument are invoked properly.

The input program pass-by-ref.cc is generated in the test's output
directory.  The input program pass-by-ref-2.cc is manually-written.

Tests have been verified on the X86_64 architecture with
GCC 7.4.0, 8.2.0, and 9.2.1.

gdb/testsuite/ChangeLog:
2019-12-20  Tankut Baris Aktemur  <tankut.baris.aktemur@intel.com>

	* gdb.cp/pass-by-ref.cc: Delete.  Generated in the output
	directory instead.
	* gdb.cp/pass-by-ref.exp: Extend with more cases.
	* gdb.cp/pass-by-ref-2.cc: New file.
	* gdb.cp/pass-by-ref-2.exp: New file.

Change-Id: Ie8ab1f260c6ad5ee4eb34b2c1597ce24af04abb6