testbench: rename process_suite.c to self_suite.c

Etc, etc
testbench: add parens around expr in fail_unless()

Oopsy.
testbench: self: add "pg" test case for test pagers

Currently, it's just the DELAY_LABEL mechanism test.
testbench: space: fix large_flush last test point

By making it more permissive of faults not related to poke()/peek().
testbench: string: clean up diags & add test TODOs