Noir docs updates

[critesjosh]

From Mike: https://aztecprotocol.slack.com/archives/C0183F0V42V/p1713438297374849?thread_ts=1713438287.652009&cid=C0183F0V42V

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1. Noir Docs: accessing pages with trailing / leads to different internal refs #296
   +0
   
2. [docs] Noir performance considerations #300
   Noir Docs documentation +2
   
3. Epic: Document how to document in noir/docs/README.md noir-lang/noir#4940
   1 of 4
   documentation enhancement good first issue +3
4. remove u72 ref: https://noir-lang.org/docs/noir/concepts/unconstrained/#example
5. explain that you can use 0x prefix to hex
6. pow_32 should explain why the number "32" is in the name
7. Can I use underscores to "comma-separate" long numbers?
8. contradiction in arrays docs about multiple dimensional arrays
9. The "nargo" help is tucked away in a "Reference" tab at the bottom of the left pane - I found myself wanting to find that shortly after installing nargo and creating a projec. Perhaps move it up, and make the word "nargo" stand out as a top-level section name?
10. I found the Logical Operations tab a few rows down from Data Types, but it took some time. Perhaps move that tab directly below Data Types. Or maybe (this would be more effort), have a section on the supported operations within each data type page. If I'm in the Field page, it'd be nice to see the supported field operations.
11. the requirements for +,-,*,/ say "types must be private input", but I wrote a test to add two public inputs.
12. broadly indicate (in the docs) the number of constraints that a particular operation costs (ignoring cost of inserting extra lookup tables)
13. it would be nice to explain somewhere that copying doesn't cost extra constraints. E.g. if I iterate through an array and assign its elements to another array, iiuc that won't add extra constraints.
14. perhaps there needs to be a section on "Efficiency" (or some better name) relating to optimising to reduce gate counts. Common themes to explain what costs lots and what is actually 'free'.
15. A section explaining that lookup tables get inserted for certain operations.
16. How do you do a reverse loop? Answered by Jake on slack the other day, but we should add a sentence to the for section.
17. If my for loop is for i in 1..(N-1) does it evaluate N-1 every loop, or just once? Just once, at compile time, apparently. Suggest explaining this in docs.
18. Explain that Field::to_le_bits does only the minimum number of loops needed to convert the field. Very nice, but we should explain this.
19. Write a section to explain that a nice 'hack' to measuring the constraints of library functions is to create an accompanying contract package (in a workspace), write lots of functions within the body of that contract, and then nargo info --package my_contract.
20. Please can we have a section on recursive functions (a function calling itself). I don't mean recursive snarks. I mean the traditional meaning of recursive. Apparently there's a limit to how many recursive calls are possible. What's this limit?