[ EPIC ] Create/move pages for "Analyze Results" section

[javabster]

To have docs reflect the Qiskit patterns structure better we need some more content that supports users in the post-processing step of the patterns.

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1. [ NEW PAGE ] Serialising job results #840
   content 📄 needs discussion 💬 on hold ⏸️ +3
   
2. [ NEW PAGE ] Retrieving and saving results #842
   0 of 1
   content 📄 needs discussion 💬 on hold ⏸️ +3
   
3. [ NEW PAGE ] Visualising results #841
   0 of 2
   content 📄 needs discussion 💬 on hold ⏸️ +3
   
4. [ NEW PAGE ] DIY Readout Error Mitigation #843
   content 📄 needs discussion 💬 +2
   
5. create tab in top nav bar

[kevinsung]

We could call out the circuit knitting toolbox: https://qiskit-extensions.github.io/circuit-knitting-toolbox/

[frankharkins]

This is complete