Improve PR builder

[JackPGreen]

While investigating a build failure I noticed several areas of improvement:

• The download-rc.js file duplicates the code for downloading each JAR
  • should be centralised
• Log messages are not correct, prints both regardless:
  • Starting Remote Controller ... enterprise ...
  • Starting Hazelcast Remote Controller ... oss ...
• The RCD logs are not viewable during a PR builder execution (making debugging startup failures tricky)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.43%. Comparing base (67b3f7a) to head (f715110).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1553      +/-   ##
==========================================
- Coverage   93.46%   93.43%   -0.03%     
==========================================
  Files         466      466              
  Lines       16628    16628              
  Branches     1350     1350              
==========================================
- Hits        15541    15537       -4     
- Misses        796      797       +1     
- Partials      291      294       +3     

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[nishaatr]

Looks ok to me
Good change!