[Feature] Enable variable support for the savepoint path

[CuteShaos]

Enable variable support for saving point paths and resolve the bug in version 2.1.6 where getFinalSavepointDir did not receive a processPath return value, resulting in redundant calls and logical errors

What changes were proposed in this pull request

Issue Number: close #4278

Brief change log

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

Does this pull request potentially affect one of the following parts

• Dependencies (does it add or upgrade a dependency): no

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull Request Overview

This PR enables variable support for Flink savepoint paths and fixes a bug where the getFinalSavepointDir method did not receive the processed path return value in version 2.1.6.

• Adds variable substitution support for job names and IDs in savepoint paths
• Restructures the savepoint path resolution logic to ensure proper processing order
• Introduces a new processPath method to handle variable replacement

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[CuteShaos]

The matching result of the two writing styles is the same. The modification avoids useless captures and is more recommended.
The parameters jobName and jobId are not null