`kontrol show` crashes if more than one test match the prefix

If kontrol show is called with a prefix that matches more than one test, it crashes with ValueError: Expected a single element, found more. For example, if there are two tests, one called StartPrankTestSymbolic.testSymbolicPrank and another called StartPrankTestSymbolic.testSymbolicPrankSplit, calling kontrol show StartPrankTestSymbolic.testSymbolicPrank produces the following error:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/lucasmt/kontrol/refute-node/src/kontrol/__main__.py", line 90, in main
    execute(**vars(args))
  File "/home/lucasmt/kontrol/refute-node/src/kontrol/__main__.py", line 336, in exec_show
    output = foundry_show(
  File "/home/lucasmt/kontrol/refute-node/src/kontrol/foundry.py", line 522, in foundry_show
    contract_name, _ = single(foundry.matching_tests([test])).split('.')
  File "/home/lucasmt/pyk/refute-node/src/pyk/utils.py", line 272, in single
    raise ValueError('Expected a single element, found more', fst, snd)
ValueError: ('Expected a single element, found more', 'test%StartPrankTestSymbolic.testSymbolicPrankSplit(address)', 'test%StartPrankTestSymbolic.testSymbolicPrank(address)')

Note that kontrol show StartPrankTestSymbolic.testSymbolicPrankSplit can be called with no problem, but there is no way to display the KCFG for StartPrankTestSymbolic.testSymbolicPrank, since its name is a strict prefix of the other test.

Some alternatives on how to handle this:

• Require the argument to kontrol show to be the full name of the test, not just a prefix.
• Keep the current behavior by default, but add an option (e.g. --full-name) to match the full name instead. Rewrite the error message above to suggest this as an option to the user.
• Print the KCFGs for all tests that match the prefix (might be hard to read and confusing if the KCFGs are large).

Start in src/kontrol/foundry.py at foundry_show and follow the call from exec_show in src/kontrol/main.py. Reproduce the prefix collision with the two test names in the report and inspect the matching behavior that reaches pyk/utils.py. Done means kontrol show handles a test name that is a strict prefix without raising the reported ValueError, according to the selected behavior.