better bit-wrangling abstraction using less boilerplate

[Fe-r-oz]

I have also checked that this does not introduce any JET errors. Hopefully, this is closes #113!

• The code is properly formatted and commented.
• Substantial new functionality is documented within the docs.
• All new functionality is tested.
• All of the automated tests on github pass.

[Krastanov]

This is wonderful!

There are quite a few more places where this is used though:

• apply_noise.jl
• pauli_operator.jl
• project_trace_reset.jl
• QuantumClifford.jl
• symbolic_clifford.jl

Not all of them necessarily need to change, maybe what is done here is appropriate to only some for them.

While this is a big step towards fixing #113, I do not think it is sufficient to call it a fix. It is way less boilerplate, but it still has some amount of boilerplate. But we should merge it before worrying about improving it further -- this will already be pretty useful.

[Fe-r-oz]

Thank you for highlighting all the files. I have carefully made the changes at appropriate places. Please do cross check them again as these bit masks are used in the critical places. Since .xz is an unsighed vector for paulis and .xzs is unsighed matrix for stabs, using AbstractArray{<:Unsighed} helps cover these two cases. Although, UInt64 is used, but I have kept to Unsighed as in some places when Unsighed was used for type of Tₘ.

I think the PR is ready for review. Thank you.