Lazy RUM raw event creation in event generator methods

[0xnm]

What does this PR do?

This PR does a bit of the optimization for the methods in RumEventExt: when random RUM raw event needs to be created, we are avoiding creating all of them and then selecting only one, but instead selecting the type and then creating only the selected one.

This gives a benefit for the tests where a lot of events are created. For example, for the RumViewScopeTest#M produce event safe for serialization W handleEvent() where there is a 1000 iterations loop to call RumMonitor#handleEvent this change is reducing execution time from 15s to 2s (and it will be much less redundant objects created, less work for GC).

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Make sure you discussed the feature or bugfix with the maintaining team in an Issue
• Make sure each commit and the PR mention the Issue number (cf the CONTRIBUTING doc)

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.36%. Comparing base (a1b97be) to head (0b9e2ac).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2363      +/-   ##
===========================================
+ Coverage    70.26%   70.36%   +0.10%     
===========================================
  Files          743      743              
  Lines        27681    27676       -5     
  Branches      4629     4630       +1     
===========================================
+ Hits         19449    19474      +25     
+ Misses        6937     6921      -16     
+ Partials      1295     1281      -14     

see 29 files with indirect coverage changes