Support realm role attributes update

[oriddd]

What this PR does / why we need it:
This PR fixes a bug where attributes are being overridden instead of merged.

PR Readiness Checklist:

• the CHANGELOG.md release notes have been updated to reflect any significant (and particularly user-facing) changes introduced by this PR
  Managed.md was updated.

[sonarcloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (e2af319) 95.53% compared to head (0b1856e) 95.70%.
Report is 33 commits behind head on main.

Files	Patch %	Lines
...sys/keycloak/config/service/RoleImportService.java	70.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #991      +/-   ##
============================================
+ Coverage     95.53%   95.70%   +0.16%     
- Complexity     1324     1367      +43     
============================================
  Files            78       80       +2     
  Lines          4279     4376      +97     
  Branches        477      494      +17     
============================================
+ Hits           4088     4188     +100     
- Misses           91       93       +2     
+ Partials        100       95       -5     

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