Implement SVR and SVR kernels with Enum. Add tests for argsort_mut

[Mec-iS]

Fixes #301 WONTFIX because of what is explained in the issue's comment

Fixes #304 see commit below

Prepare for release v0.4.2

Checklist

• My branch is up-to-date with development branch.
• Everything works and tested on latest stable Rust.
• Coverage and Linting have been applied

Current behaviour

• Implement SVR kernels as enumerator
• basic svr and svr_params implementation
• Implement search grid for SVR. Add documentation.
• Fix serde configuration in cargo clippy
• Add tests for sorting and add type to stack variable parameter

Changes

• BREAKING CHANGES: the interface for defining kernels is slightly changed. See tests in the src/svm/mod.rs module.

[codecov]

Codecov Report

Attention: Patch coverage is 64.70588% with 24 lines in your changes missing coverage. Please review.

Project coverage is 46.21%. Comparing base (239c004) to head (29049af).
Report is 7 commits behind head on development.

Files with missing lines	Patch %	Lines
src/svm/mod.rs	57.14%	12 Missing ⚠️
src/svm/search/svr_params.rs	75.00%	9 Missing ⚠️
src/svm/svr.rs	0.00%	2 Missing ⚠️
src/linalg/basic/arrays.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@               Coverage Diff               @@
##           development     #303      +/-   ##
===============================================
+ Coverage        45.49%   46.21%   +0.71%     
===============================================
  Files               85       86       +1     
  Lines             7254     7390     +136     
===============================================
+ Hits              3300     3415     +115     
- Misses            3954     3975      +21     

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