SI-7494 Tests for status quo

Exploit SI-6446 fix to move old pending tests for plugins to the
active pool.

Also, nuance the partest runner to allow the compiler to crash
with a FatalError if a check file is present.

Some of the plugin tests make phase assembly throw.

One of the legacy tests was moved back to pending:

There seems to be a race for who shall be deemed truly dependent.

Back to pending for you!

apm@mara:~/projects/snytt/test$ ./partest files/neg/t7494-cyclic-dependency/
Selected 1 tests drawn from specified tests

> starting 1 test in neg
ok 1 - neg/t7494-cyclic-dependency

1/1 passed (elapsed time: 00:00:04)
Test Run PASSED
apm@mara:~/projects/snytt/test$ ./partest files/neg/t7494-cyclic-dependency/
Selected 1 tests drawn from specified tests

> starting 1 test in neg
!! 1 - neg/t7494-cyclic-dependency               [output differs]
> 0/1 passed, 1 failed in neg

>>>>> Transcripts from failed tests >>>>>

> partest files/neg/t7494-cyclic-dependency
% scalac t7494-cyclic-dependency/ThePlugin.scala
% scalac t7494-cyclic-dependency/sample_2.scala
error: Cycle in compiler phase dependencies detected, phase cyclicdependency1 reacted twice!

% diff files/neg/t7494-cyclic-dependency-neg.log files/neg/t7494-cyclic-dependency.check
@@ -1 +1 @@
-error: Cycle in compiler phase dependencies detected, phase cyclicdependency1 reacted twice!
+error: Cycle in compiler phase dependencies detected, phase cyclicdependency2 reacted twice!

0/1 passed, 1 failed (elapsed time: 00:00:04)
Test Run FAILED

1 files changed, 3 insertions, 0 deletions

diff --git a/test/files/neg/t7494-multi-right-after.check b/test/files/neg/t7494-multi-right-after.check
new file mode 100644
index 0000000000..9c6fdbe91f
--- /dev/null
+++ b/test/files/neg/t7494-multi-right-after.check
@@ -0,0 +1,3 @@
+error: Multiple phases want to run right after the phase explicitouter
+Phases: erasure, multi-rafter, 
+Re-run with -Xgenerate-phase-graph <filename> to better see the problem.