Separate out primitives

[beckykd]

Addresses part of #4613

Executor changes have been moved to #5028

Changes are extensive. Files to review follow:

Files with totally new content:

• https://qiskit.github.io/documentation/pr-4640/docs/guides/get-started-with-backend-primitives
• https://qiskit.github.io/documentation/pr-4640/docs/guides/estimator-noise-management
• https://qiskit.github.io/documentation/pr-4640/docs/guides/sampler-noise-management

The rest of the changes are:

• Old content split into new files (instead of having 1 topic for all primitives, there are now individual files for Estimator, and Sampler,
• Updated / new links (due to the above)
• Updated link formatting - Links should be /docs/guides, and a lot were just ./
• Fixes to capitalization of primitive names, and use of "the" in front of primitive names

You can probably just ignore the files with changes of the third type, but you're welcome to review and commend on all 127 changed files if you so desire :)

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[jyu00]

I think we are almost there! Two extra comments:

1. This PR no longer contains the Executor pages, but Executor section still shows up on the left nav.
2. Can we move the Directed execution model (beta) page to be right after Introduction to primitives? It's also an intro/overview page that seems weird to be at the bottom.

[jyu00]

I'm still seeing those stupid warnings from QiskitRuntimeService(), but I assume they'll go away once you re-run CI.

[beckykd]

I'm still seeing those stupid warnings from QiskitRuntimeService(), but I assume they'll go away once you re-run CI.
I changed the code, so they should. I'll keep an eye out!

[beckykd]

I'm still seeing those stupid warnings from QiskitRuntimeService(), but I assume they'll go away once you re-run CI.

I reran it and don't see the warnings now.

[abbycross]

💥

[abbycross]

💥 💥