[Feature] Implement Fast Convolution and Cross-Correlation

[skylarkgit]

Summary:
This pull request introduces the implementation of fast convolution and cross-correlation methods using FFT (Fast Fourier Transform). It includes:

• Implementation of fastConvolve and fastCrossCorrelate methods.
• Support for different convolution modes: full, same, and valid.
• Error handling for invalid modes.

When to Use Fast Convolution and Cross-Correlation:

• Use these methods when dealing with large datasets or signals where performance is critical.
• They are particularly beneficial in applications requiring real-time signal processing or where the convolution/cross-correlation operation is a bottleneck.
• Suitable for high-performance computing environments and scenarios involving repeated calculations on similar-sized data.

Details:

1. Fast Convolution:

   • Implements the fastConvolve method which performs convolution using FFT.
   • Supports full, same, and valid modes.
   • Includes proper error handling for invalid modes.

2. Fast Cross-Correlation:

   • Implements the fastCrossCorrelate method which performs cross-correlation using fastConvolve.
   • Supports full, same, and valid modes.

Changes Made:

• Added fastConvolve and fastCrossCorrelate methods in the respective classes.
• Added detailed comments and documentation to explain the methods and parameters.
• Included error handling for invalid modes.

Testing:

• Tested the methods with different modes (full, same, valid) to ensure correctness.