Text this: A Comprehensive Study of the Synthesis, Spectral Characteristics, Quantum–Chemical Molecular Electron Density Theory, and In Silico Future Perspective of Novel CBr₃-Functionalyzed Nitro-2-Isoxazolines Obtained via (3 + 2) Cycloaddition of (<i>E</i>)-3,3,3-Tribromo-1-Nitroprop-1-ene