Fixed the path-to-smt-solver bug in windows

[vb213]

Intended Change

The specified path to a smt solver has been assembled incorrectly from the user input but still got cached in the proofIndependentSettings.props file. This caused a crash when restarting KeY. Now,

1. the path is assembled correctly and
2. an invalid smt solver path in proofIndependentSettings.props will be ignored, thereby avoiding a crash on program start.

Type of pull request

• [ X] Bug fix (non-breaking change which fixes an issue)
• [ ] Refactoring (behaviour should not change or only minimally change)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] There are changes to the (Java) code
• [ ] There are changes to the taclet rule base
• [ ] There are changes to the deployment/CI infrastructure (gradle, github, ...)
• [ ] Other:

Ensuring quality

• [ ] I made sure that introduced/changed code is well documented (javadoc and inline comments).
• [ ] I made sure that new/changed end-user features are well documented (https://github.com/KeYProject/key-docs).
• [ ] I added new test case(s) for new functionality.
• [ ] I have tested the feature as follows: ...
• [X ] I have checked that runtime performance has not deteriorated.

The contributions within this pull request are licensed under GPLv2 (only) for inclusion in KeY.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 59.09091% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 37.91%. Comparing base (7254776) to head (f423328). Report is 21 commits behind head on main.

:exclamation: Current head f423328 differs from pull request most recent head b5f8c17. Consider uploading reports for the commit b5f8c17 to get more accurate results

Files	Patch %	Lines
.../key/smt/solvertypes/SolverTypeImplementation.java	59.09%	4 Missing and 5 partials :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3434 +/- ## ============================================ + Coverage 37.86% 37.91% +0.05% + Complexity 17079 17071 -8 ============================================ Files 2092 2076 -16 Lines 127596 127026 -570 Branches 21478 21385 -93 ============================================ - Hits 48316 48168 -148 + Misses 73355 72952 -403 + Partials 5925 5906 -19 ```

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