mem: Deprecate SlavePort and MasterPort classes

mem: Deprecate SlavePort and MasterPort classes

After this change, if you use these classes or inherit from these
classes, the compiler will now give you a warning that these names are
deprecated. Instead, you should use ResponsePort and RequestPort,
respectively.

This patch simply deprecates these names. The following patches will
convert all of the code in gem5 to use these new names. The first step
is converting the class names and the uses of these classes, then we
will update the variable names to be more precise as well.

Change-Id: I5e6e90b2916df4dbfccdaabe97423f377a1f6e3f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/32308
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>