tests: Removed "tests/long"

Tests/resources contained within "tests/long" have been migrated to the
testlib framework.

Change-Id: I014edfac72f5d0df22abf4d4c7a69976b57d785a
Issue-on: https://gem5.atlassian.net/browse/GEM5-109
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27630
Tested-by: Gem5 Cloud Project GCB service account <345032938727@cloudbuild.gserviceaccount.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
139 files changed