tests: Don't treat new stats as a cause for failures

We currently fail the stat diff stage of tests if there are new
stats. This is usually undesirable since this would require any change
that adds a stat to also update the regressions.

Change-Id: Ieadebac6fd17534e1b49b6b9a1d56f037a423325
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/3962
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Jason Lowe-Power <jason@lowepower.com>

tests: fix diff-out script for op/inst stat changes.

diff-out: clean up options
Make diff-out sort stats changes by percentage
by default, with '-a' to use current alpha sort
(instead of requiring '-p' to sort by percentage).
Other minor options cleanup too.

stats: fix stats diff script
Previously the return value ignored missing/added stats,
making the regressions not tell you when you needed to
update the reference stats because of these changes.
Also stop filtering distributions when reporting these;
not sure why we did that in the first place.
Also get rid of obsolete hacks for the "fetch-loss" stats
that have been gone for a long time.

diff-out:
Don't consider it a success if no stats at all were found.

tests/diff-out:
Don't consider it a success if no stats at all were found.

Put regression tests back into m5. They are located in the "tests" directory. The directory output and reference outputs have changed slightly. Now the directory is ALPHA_SE/test/<test>/<cpu_model>/, and for the reference stats <test>/ref/<arch>/<cpu_model>

Right now only non-SMT SE regression tests have been added back in. The rest are pending getting SMT working, and consolidating the FS configuration files.

Eventually support for different OSs can be added so you can specify which versions of the binary you want to run from one config file.

Note: mp-test1 doesn't have any reference stats because MP mode doesn't currently work. The test itself should probably work once the code is fixed.

SConstruct:
Updates to allow for regression tests to work via the command line "scons build/ALPHA_SE/test/debug/quick" and such once again.
src/cpu/SConscript:
Keep a list of SMT supporting CPUs so that the regression tests can easily specify which CPUs to use if they are SMT only.