Swift direct C++ interop (aka Linux support)

[danpalmer]

This PR was superseded by #568 which implemented the Swift support based on the C bindings to work around limitations in the Swift C++ interop.

This is a WIP implementation of a direct Swift to C++ implementation. It includes the necessary modulemap for Swift to understand the C++ codebase, the SPM updates, and a WIP port of the code in USearchObjective to Swift.

Unfortunately this doesn't work. There are two main issues:

1. Swift/C++ interop does not bridge nested types in generic types, this means the result types can't be bridged. This likely requires a non-trivial refactor, or an intermediate bridge to be built in C++. This is unfortunately beyond my very limited C++ abilities.
2. An ambiguity in simsimd around the sqrt function available. I commented out the offending lines in order to progress, but it likely needs to be solved in that library.

Next steps:

I can't complete this, however if someone is willing to contribute just the necessary C++ code to meet the Swift interop requirements, I'm happy to finish up the Swift, refactor USearchIndex and Index+Sugar, get the tests working, etc.

[danpalmer]

Closing in favour of #568.