Concatenate Quantum Registers

Required prerequisites

• Search the issue tracker to check if your feature has already been mentioned or rejected in other issues.

Describe the feature

I suggest there should be a function that allows to merge quantum registers.
With the current features of cudaq one, for instance, can do the following:

 __qpu__ void myFucntion(cudaq::qview<> qc)
{
    cudaq::qview<> qc_1 = qc.front(qc.size()-1);
    cudaq::qubit &q = qc[qc.size()-1];
    DoSomething(qc_1,q);
}

namely I can separate a quantum register. However I cannot merge quantum registers. This can be very useful when one has numerous quantum functions which handle the input registers differently. Suppose I have a function that works as follows:

__qpu__ void Func1(cudaq::qview<> qc)
{    
   cudaq::x(qc);
}

Then I have another function that takes as input two quantum registers. Inside this function I want to apply Func1() to both the two registers together. In this case there is not, to my knowledge, a possibility to merge the two input quantum registers and apply the other function to the register which is the result of the merge. What I would liike to do is:

__qpu__ void Func2(cudaq::qview<> qc_1, cudaq::qview<> qc_2)
{
    cudaq::y(qc_1);
    cudaq::qview<> qc_merge = cudaq::concatenate(qc_1,qc_2);
    Func1(qc_merge);
}

Is there the option to do so? If yes what is it? If not, it would be nice to have it.
Best regards!

Start by reading the existing cudaq::qview interface, especially the qc.front(qc.size()-1) usage shown in the issue, and check whether register-combination support already exists. Define and validate the behavior needed for concatenating qc_1 and qc_2 so Func1(qc_merge) can operate on the result.