tests: cleanup all SE tests previously moved to gem5-resources

tests: cleanup all SE tests previously moved to gem5-resources

The move was done at:
https://gem5-review.googlesource.com/c/public/gem5-resources/+/32074

All files keep exact same name, or are obvious renames like underscore to
-. threads/ is the only non obvious and remaps to src/simple/std_thread.cpp

Only m5-exit is left because it does squashfs generation which wasn't yet
moved.

Change-Id: I72ad104c9311c2f81af49458bdd44e24a6bafc0a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/34476
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>