NIFI-12297 Standardize File Path resolution in Persistence Providers

[exceptionfactory]

Summary

NIFI-12297 Standardizes file path resolution in the NiFi Registry File System Bundle and Flow Persistence Providers, as well as the file-backed Registry client for system tests.

These changes replace string concatenation and related strategies with a standard approach using Java NIO Paths. Using Paths ensures consistent directory separator handling and path normalization.

Additional changes include updating related unit tests to reuse shared identifier values.

Tracking

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Issue Tracking

• Apache NiFi Jira issue created

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• Pull Request title starts with Apache NiFi Jira issue number, such as NIFI-00000
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Build

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  • JDK 21

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[markap14]

Thanks for the cleanup here @exceptionfactory all looks good to me. +1 will merge.

[markap14]

Merged to main @exceptionfactory but it conflicts with the support/nifi-1.x branch. Jira targets that branch as well. If you'd like to have it merged to the support branch, do you mind pushing a new PR for that?