Remove MasterService class

[andrross]

This has been deprecated and is replaced by ClusterManagerService.

Related Issues

Part of #5214

Check List

• Functionality includes testing.
• API changes companion pull request created, if applicable.
• Public documentation issue/PR created, if applicable.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[github-actions]

✅ Gradle check result for c1c8d39: SUCCESS

[codecov]

Codecov Report

Attention: Patch coverage is 85.19481% with 57 lines in your changes missing coverage. Please review.

Project coverage is 72.25%. Comparing base (e6fc600) to head (c1c8d39).
Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
...nsearch/cluster/service/ClusterManagerService.java	85.19%	41 Missing and 16 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #17151      +/-   ##
============================================
- Coverage     72.34%   72.25%   -0.09%     
+ Complexity    65481    65454      -27     
============================================
  Files          5300     5299       -1     
  Lines        304330   304318      -12     
  Branches      44141    44140       -1     
============================================
- Hits         220158   219900     -258     
- Misses        66093    66409     +316     
+ Partials      18079    18009      -70     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.