format_type can now format range_typet

[kroening]

This adds formatting for range_typet as { from, ..., to }.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.23%. Comparing base (4c59d28) to head (5826a8e).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #8473   +/-   ##
========================================
  Coverage    78.22%   78.23%           
========================================
  Files         1726     1727    +1     
  Lines       189038   189050   +12     
  Branches     18467    18467           
========================================
+ Hits        147874   147898   +24     
+ Misses       41164    41152   -12     

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