line breaking hints in the ViewString method for lists

[ThomasBreuer]

Description

Up to now, ViewObj and ViewString behaved differently for lists,
due to the prescribed line breaking hints \< and \>.
This was a reason why new ViewString methods for complicated GAP objects
were likely to produce output that looked different from ViewObj output.

With the proposed change, the line breaking hints in the ViewObj and ViewString methods
for finite lists are made consistent with those that appear in the kernel function PrintListDefault.

Only a few test examples are affected by this change, they have been adjusted.

(I think that after this change, it will make sense to add more ViewString methods.)

An open problem is that ViewString cannot handle self-referential objects.
Note that the GAP kernel does some bookkeeping in the case of ViewObj;
an analogous mechanism would be possible also for ViewString.

Text for release notes

Fixed the line breaking hints in the ViewString method for finite lists.

Checklist for pull request reviewers

• proper formatting

If your code contains kernel C code, run clang-format on it; the
simplest way is to use git clang-format, e.g. like this (don't
forget to commit the resulting changes):

git clang-format $(git merge-base master)

• usage of relevant labels

  1. either release notes: not needed or release notes: to be added
  2. at least one of the labels bug or enhancement or new feature
  3. for changes meant to be backported to stable-4.X add the backport-to-4.X label
  4. consider adding any of the labels build system, documentation, kernel, library, tests

• runnable tests

• adequate pull request title

• well formulated text for release notes

• relevant documentation updates

• sensible comments in the code

[coveralls]

Coverage increased (+0.001%) to 85.147% when pulling 12801e4 on ThomasBreuer:TB_ViewString_lists into 1afd3f7 on gap-system:master.