RFC tests reorg

[evelikov]

While going through the earlier test PRs (#258 and #375), a few things of varying annoyance stood out. Each of these is mostly independent, so one can thumbs up/down individually or as a whole:

• inconsistent cleanups in error path - mostly addressed by latter PR, finish and merge
• custom checks vs assert_return() - ditto
• test names (as per test-foo --list) starting with test_ (61) vs not (55) - remove the prefix
• arbitrary/non-descriptive test names (alias_1, from_alias, etc) - use util_alias, libkmod_new_from_alias, aka $top-level-dir_testname or $tool_testname
• ^^ for filenames (test-blacklist.c, test-dependencies.c, test-loaded.c, etc) - use test-libkmod-foobar.c
• multiple-files-per-tool (test-modprobe, test-weakdep, etc) - merge into one
• one-test-per-file (mostly likmod API) - merge, unless it causes problems
• dozen+ test binaries, non-unique testnames (practically identical/duplicated test_remove), manually running tests (tab completion doesn't work in sh -c 'source ....) - fold into single binary

@lucasdemarchi @stoeckmann do let me know what you think. All of these are a net positive IMHO, with the* minus being the temporary churn. If you see any item as a potential deterrent from adding more test, please let me know.