Add extended basis rotation operations for OpenFHE dialect

[toprakmurat]

Summary

This PR adds support for extended basis operations in the OpenFHE dialect, allowing the use of an optimization technique where multiple rotations are performed in a larger (P*Q) CRT basis and combined before a single key_switch_down converts the result back to the normal (Q) basis.

This is groundwork for addressing #2519.

New Operations

Operation	Description
openfhe.fast_rotation_ext	Fast rotation in extended P*Q basis (defers key switching)
openfhe.key_switch_down	Converts ciphertext from extended to normal basis
openfhe.add_ext	Addition of ciphertexts in extended basis
openfhe.add_ext_inplace	In-place addition in extended basis
openfhe.mul_ext	Multiplication in extended basis (uses EvalMultNoRelin)

[toprakmurat]

I'd appreciate feedback on the operation signatures in OpenfheOps.td (are the arguments and attributes appropriate?), whether we need a distinct type for extended-basis ciphertexts or can reuse Openfhe_Ciphertext, and any concerns with the overall approach before I proceed with implementing the conversion pass and optimization patterns to push key_switch_down later in the IR.

[asraa]

Thank you so much! Great job on starting the tablegen and making a small PR

[asraa]

It looks like from https://github.com/openfheorg/openfhe-development/blob/aa391988d354d4360f390f223a90e0d1b98839d7/src/pke/include/cryptocontext.h#L2438

that the arguments needed are (cryptoContext, input, index, precomputedDigitDecomp, addFirst) - in other words i don't think you neeed cyclotomicOrder anymore.

[j2kun]

+1, I submitted the patch to remove that argument, though we should double check it's in the OpenFHE version we're depending on

[asraa]

your patch was only for the regular evalfastrotation, this API was unchanged and i guess never had that m param

[asraa]

I wonder if you can share a function with EvalFastRotation? The code is very very similar.