Split up vector_swizzle tests into smaller chunks to improve compilation times

[lbushi25]

The vector swizzle tests are failing to compile on machines with 16 GB of RAM due to the huge size of some of the test .cpp files that are generated by the scripts. This PR makes the necessary changes to enforce splitting of these test files into smaller and more manageable files that can be compiled without requiring a large memory footprint. As of the time of this writing, I've chosen the number of batches aka chunks to be 32 so that each large file will be subdivided into 32 smaller files. I chose this number because with 16 chunks I was seeing flaky results where a compilation would succeed or fail depending on the state of the machine at the time of compilation. With 32 however, compilation was succeeding constantly. Nevertheless, this can easily be adjusted according to our needs.

[keryell]

Thanks!
Your PR description is an interesting design argumentation which should appear somewhere in some comments to avoid being lost.