Remove Directive::ToLeRadix

[TomAFrench]

We currently have a single variant of the directive opcode which we use for bit/byte decompositions.

If we perform the decomposition in a brillig function then we can remove this superfluous opcode (and solver) from the ACVM and just have it in the brillig VM.

[TomAFrench]

This would be implemented by writing a new brillig directive similar to those in https://github.com/noir-lang/noir/blob/master/compiler/noirc_evaluator/src/brillig/brillig_gen/brillig_directive.rs. We could then have the acir-gen code emit a call to this rather than a directive opcode.

Actual removal of the directive opcode would need to be done later in aztec-packages.

[TomAFrench]

Closed by AztecProtocol/aztec-packages#9970