Add Fourier-Extension CKKS functional bootstrapping from 2026/367

[yspolyakov]

Add the functional bootstrapping method for continuous variables from 2026/367 (EUROCRYPT'26) to the CKKS implementation in OpenFHE. Use https://github.com/fyhssgss/FEFBS as the starting point.

The plan for initial steps.

1. Create a feature branch in openfhe-development.
2. Add unit tests for the cases that are supported.
3. Add support for UNIFORM_TERNARY + unit tests for it.
4. Add support for FLEXIBLE* + FIXEDAUTO + unit tests for it.