Add support for Receiver with multiple Processing Pipelines

A receiver would have a variant of pipelines that can be selected at runtime.

std::variant<noop, smx, avg> pipeline; // Receiver can switch to any of these pipelines

A single acquisition can then be configured to switch processing after a given nb of frames. A processing sequence would be define as:

struct proc_step {
    int nb_frames;
    proc_enum proc;
    /* ... */ proc_params ;
};

// processing sequence
std::vector<proc_sequence> proc_params{
   { 100, proc_enum::noop, { ... }}, // warmup 
   { 1000, proc_enum::avg, { ... }}, // pedestal measurement
   { -1, proc_enum::smx , { ... }}, // experiment
};