Limit verbosity of fizzy-spectests

[chfast]

The output from fizzy-spectests is quite large as it reports status of every executed test case. I expect users are mostly interested in failures. Some ideas how to improve it.

1. Skip PASSED reports by default. Easy to implement.
2. Repeat status of each file in the end. This will allow at least quickly find the file with failures and repeat the run on the subset of files.
3. Use "dot notation" per file. Each test result is represented by a single character. E.g.

   binary.wast: ......F.....s.....
   Line 98: assert_return FAILED Incorrect returned value. Expected: 9219994337134247936 (0x7ff4000000000000) Actual: 0 (0x0)
   Line 99: assert_return SKIPPED Unsupported feature: Floating point instruction.
   

[axic]

I like a combination of 1. and 3.:

• display it like you propose in 3.
• do not display SKIPPED by default, but add an option --show-skipped to show them