P2944R3: Comparisons for `reference_wrapper`

[ldionne]

Link: https://wg21.link/P2944R3

• Comparisons for reference_wrapper
• Constrained equality

BEGIN-RST-NOTES
The changes to ``tuple``'s equality overload from P2165R4 are not yet implemented.
END-RST-NOTES

[Zingam]

This is partially implemented in:
#88384
I'm assigning this to me for later.
If someone feels like to take it over please feel free to reassign it.

[miroslavavramov]

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