Moved the modified reference server from the unit test to its own file

[ThomasNehring]

Also moved the modified (server side) session, the modified session manager and the modified master node manager to the same file.

Proposed changes

The unit test ContinuationPointInBatchTest was developed together with a modified reference server which allows to change the limit for (browse) ContinuationPoints during the test.
To allow easier reuse of this modified reference server and to make the unit test better readable, the modified reference server is now moved into it's own file.

Related Issues

• Fixes # (n/a)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.77%. Comparing base (6291ed6) to head (63ced91).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2725      +/-   ##
==========================================
+ Coverage   54.75%   54.77%   +0.01%     
==========================================
  Files         349      349              
  Lines       65866    65866              
  Branches    13493    13493              
==========================================
+ Hits        36067    36080      +13     
+ Misses      25886    25878       -8     
+ Partials     3913     3908       -5     

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[mregen]

@ThomasNehring please merge with master to ensure latest changes were captured