Refactoring: Compiler to return new structure for several machines

[leolara]

We need to start the path that allows multiple machines. This is a complex refactoring, and from the SBPIR on we will build new compiler to the plonkish IR. But this is not in this task.

We should allow the main compiler src -> SBPIR to return several machines.

For that I would:

1. rename the current compiler::compile function to compiler::compile_legacy and compiler::CompilerResult to compiler::CompilerResultLegacy. We need this so the previous examples and tests keep working. It should be easy with a refactoring tool like in vscode.
2. Rename sbpir::SBPIR to sbpir::SBPIRMachine.
3. Create a new sbpir::SBPIR that contains a hashmap of uuid -> SBPIRMachine and another hashmap from identifier -> uuid.
4. Create a new compiler::compile that can take a source code with several machines and returns a new compiler::CompilerResult that contains the new sbpir::SBPIR

[leolara]

Even, better SBPIR renamed to SBPIRLegacy and a copy of SBPIR becomes SBPIRMachine that we will be able to modify SBPIRMachine a lot, and create a new plonkish compiler.

Eventually this will end up removing the SuperCircuits that are not that good design, but we inherited from zkEVM.

[alxkzmn]

Implemented in #284