Fix data node metrics data stream generation

[moesterheld]

Description

Fixes generation of data stream system indices with a wrong number of replicas on single-node setups (fixes #19010) and generation of metrics data stream and ism settings only from the leader node (fixes #18830)

Motivation and Context

fixes #18830 fixes #19010

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Refactoring (non-breaking change)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [x] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [x] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.